Applications of Photonics, Laser, Plasma and Radiation Physics

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Entropy entropy	2.1	4.9	1999	22.4 Days	CHF 2600
Photonics photonics	2.1	2.6	2014	14.8 Days	CHF 2400
Physics physics	1.5	3.0	2019	33.6 Days	CHF 1400
Plasma plasma	1.9	2.3	2018	22.9 Days	CHF 1400
Universe universe	2.5	4.3	2015	21.8 Days	CHF 2400
Fractal and Fractional fractalfract	3.6	4.6	2017	20.9 Days	CHF 2700
Condensed Matter condensedmatter	1.9	2.9	2016	21 Days	CHF 1600

17 pages, 3332 KiB

Open AccessArticle

The Suppression Effect of an Imaging System on the Geometric Tilt-to-Length Coupling in a Test Mass Interferometer

by Jia Shen, Shaoxin Wang, Keqi Qi, Mengyang Zhao, Heshan Liu, Ran Yang, Pan Li, Wei Tao, Ziren Luo and Ruihong Gao

Photonics 2024, 11(7), 638; https://doi.org/10.3390/photonics11070638 - 3 Jul 2024

Viewed by 724

Abstract

Tilt-to-length (TTL) coupling noise arises from angular misalignments of interfering beams in optical path length (OPL) measurements and significantly impacts the accuracy of interferometry measurement systems. This paper focuses on geometric TTL coupling in a test mass (TM) interferometer and examines how an [...] Read more.

Tilt-to-length (TTL) coupling noise arises from angular misalignments of interfering beams in optical path length (OPL) measurements and significantly impacts the accuracy of interferometry measurement systems. This paper focuses on geometric TTL coupling in a test mass (TM) interferometer and examines how an imaging system influences TTL noise suppression. First, the analytical expression of the geometric TTL coupling in a TM interferometer with alignment errors is derived and confirmed through numerical simulation. Subsequently, an imaging system is incorporated into the geometric model and the corresponding analytical expressions are obtained under two common conjugate relationships. Nevertheless, the TTL coupling remains beyond the requirement of TM interferometer, as the residual TTL coupled with alignment errors persists even with the imaging system. Therefore, an optimal position of the imaging system capable of eliminating the second-order term of the TTL coupling is determined. Meanwhile, the first-order term can be mitigated through in-orbit calibrations. These findings offer valuable guidance for the design and adjustment of imaging systems in space-borne gravitational wave detection missions, which require high-precision laser interferometry. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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16 pages, 7405 KiB

Open AccessArticle

Mid-Infrared 2.79 μm Band Er, Cr: Y₃Sc₂Ga₃O₁₂ Laser Transmission Anti-Bending Low-Loss Anti-Resonant Hollow-Core Fiber

by Lei Huang, Peng Wang, Yinze Wang, Tingqing Cheng, Li Wang and Haihe Jiang

Photonics 2024, 11(5), 432; https://doi.org/10.3390/photonics11050432 - 5 May 2024

Cited by 1 | Viewed by 1449

Abstract

A large core size and bending resistance are very important properties of mid-infrared energy transfer fibers, but large core sizes usually lead to the deterioration of bending properties. A negative-curvature nested node-free anti-resonant hollow-core fiber (AR-HCF) based on quartz is proposed. It was [...] Read more.

A large core size and bending resistance are very important properties of mid-infrared energy transfer fibers, but large core sizes usually lead to the deterioration of bending properties. A negative-curvature nested node-free anti-resonant hollow-core fiber (AR-HCF) based on quartz is proposed. It was made by adding a nested layer to a previous AR-HCF design to provide an additional anti-resonance region while keeping the gap between adjacent tubes strictly correlated with the core diameter to produce a node-free structure. These features improve the fiber’s bending resistance while achieving a larger core diameter. The simulation results show that the radial air–glass anti-resonant layer is increased by the introduction of the nested anti-resonant tube, and the weak interference overlap between the fiber core and the cladding mode is reduced, so the fiber core’s limiting loss and sensitivity to bending are effectively reduced. When the capillary wall thickness t of the fiber is 0.71 μm, the core diameter D is 70 μm, the ratio of the inner diameter of the cladding capillary to the core diameter d/D is 0.62, the diameter of the nested tube is d₀ = 29 μm, the fiber has a lower limiting loss at the wavelength of 2.79 μm, and the limiting loss is 3.28 × 10⁻⁴ dB/m. At the same time, the optimized structure also has good bending resistance. When the bending radius is 30 mm, the bending loss is only 4.72 × 10⁻² dB/m. An anti-bending low-loss micro-structure hollow fiber with a bending radius of less than 30 mm was successfully achieved in the 2.79 μm band. An anti-bending low-loss anti-resonant hollow-core fiber with this structure constitutes a reliable choice for the light guiding system of a 2.79 μm band Er, Cr: YSGG laser therapy instrument. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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15 pages, 5041 KiB

Open AccessArticle

HoloDiffusion: Sparse Digital Holographic Reconstruction via Diffusion Modeling

by Liu Zhang, Songyang Gao, Minghao Tong, Yicheng Huang, Zibang Zhang, Wenbo Wan and Qiegen Liu

Photonics 2024, 11(4), 388; https://doi.org/10.3390/photonics11040388 - 21 Apr 2024

Viewed by 1142

Abstract

In digital holography, reconstructed image quality can be primarily limited due to the inability of a single small aperture sensor to cover the entire field of a hologram. The use of multi-sensor arrays in synthetic aperture digital holographic imaging technology contributes to overcoming [...] Read more.

In digital holography, reconstructed image quality can be primarily limited due to the inability of a single small aperture sensor to cover the entire field of a hologram. The use of multi-sensor arrays in synthetic aperture digital holographic imaging technology contributes to overcoming the limitations of sensor coverage by expanding the area for detection. However, imaging accuracy is affected by the gap size between sensors and the resolution of sensors, especially when dealing with a limited number of sensors. An image reconstruction method is proposed that combines physical constraint characteristics of the imaging object with a score-based diffusion model, aiming to enhance the imaging accuracy of digital holography technology with extremely sparse sensor arrays. Prior information of the sample is learned by the neural network in the diffusion model to obtain a score function, which alternately constrains the iterative reconstruction process with the underlying physical model. The results demonstrate that the structural similarity and peak signal-to-noise ratio of the reconstructed images using this method are higher than the traditional method, along with a strong generalization ability. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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14 pages, 15723 KiB

Open AccessArticle

by Aleksander Y. Fedorenko, Almikdad Ismaeel, Ilya O. Orekhov, Dmitriy A. Dvoretskiy, Stanislav G. Sazonkin, Lev K. Denisov and Valeriy E. Karasik

Photonics 2024, 11(4), 387; https://doi.org/10.3390/photonics11040387 - 21 Apr 2024

Cited by 2 | Viewed by 1126

Abstract

An Er-doped all-fiber ultrashort pulse laser with positive total net-cavity group-velocity dispersion is demonstrated based on a hybrid mode-locking mechanism ensured by single-walled carbon–boron–nitrogen nanotubes with coaction of the nonlinear polarization evolution effect. The generation regime with a similariton-like spectrum is obtained. The [...] Read more.

An Er-doped all-fiber ultrashort pulse laser with positive total net-cavity group-velocity dispersion is demonstrated based on a hybrid mode-locking mechanism ensured by single-walled carbon–boron–nitrogen nanotubes with coaction of the nonlinear polarization evolution effect. The generation regime with a similariton-like spectrum is obtained. The spectrum width is ~31.5 nm, and the minimal pulse duration is ~294 fs at full width at half maximum. The average output power is ~3.2 mW, corresponding to 0.376 nJ pulse energy and 1.25 kW peak power. The fundamental pulse repetition rate is ~8.5 MHz, with a signal-to-noise ratio of 60 dB. The standard deviation of average output optical power stability, measured for 12 h, is about ~1% RMS, and the maximum level of relative intensity noise (RIN) does not exceed <−120 dBc/Hz in the 30 Hz–1 MHz frequency range. To prove the similariton-like regime generation, we also studied numerically and experimentally the pulse evolution during propagation through a laser resonator and output single-mode fiber with anomalous dispersion. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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15 pages, 5612 KiB

Open AccessArticle

Design and Optimization of Potentially Low-Cost and Efficient MXene/InP Schottky Barrier Solar Cells via Numerical Modeling

by Mohammad Saleh N Alnassar

Condens. Matter 2024, 9(1), 17; https://doi.org/10.3390/condmat9010017 - 3 Mar 2024

Cited by 1 | Viewed by 1805

Abstract

This paper uses numerical modeling to describe the design and comprehensive analysis of cost-effective MXene/n-InP Schottky barrier solar cells. The proposed design utilizes Ti₃C₂T_x thin film, a 2D solution-processible MXene material, as a Schottky transparent conductive electrode (TCE). [...] Read more.

This paper uses numerical modeling to describe the design and comprehensive analysis of cost-effective MXene/n-InP Schottky barrier solar cells. The proposed design utilizes Ti₃C₂T_x thin film, a 2D solution-processible MXene material, as a Schottky transparent conductive electrode (TCE). The simulation results suggest that these devices can achieve power conversion efficiencies (PCEs) exceeding 20% in metal–semiconductor (MS) and metal–interlayer–semiconductor (MIS) structures. Combining the proposed structures with low-cost InP growth methods can reduce the gap between InP and other terrestrial market technologies. This is useful for specific applications that require lightweight and radiation-hard solar photovoltaics. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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11 pages, 3992 KiB

Open AccessArticle

Research on Optical Mutual Injection to Generate Tunable Microwave Frequency Combs

by Bin Wu and Qingchun Zhao

Photonics 2024, 11(3), 195; https://doi.org/10.3390/photonics11030195 - 22 Feb 2024

Cited by 2 | Viewed by 1256

Abstract

In this study, a scheme for generating tunable microwave frequency combs (MFCs) based on optical mutual injection is proposed and experimentally investigated. The scheme is based on the optical injection of lasers to generate MFCs, and constitutes a feedback loop by using dual-laser [...] Read more.

In this study, a scheme for generating tunable microwave frequency combs (MFCs) based on optical mutual injection is proposed and experimentally investigated. The scheme is based on the optical injection of lasers to generate MFCs, and constitutes a feedback loop by using dual-laser mutual injection to obtain MFCs with a large continuous bandwidth and tunable comb spacing. The experimental setup analyzes the effects of injected optical power, modulation frequency and amplitude, and wavelength detuning on the generated MFC signals. The experimental results indicate that when the single-frequency electrical signal is set to 2 GHz, flat MFCs with amplitude variations within 10 dB can be obtained by optimizing the injected power and the frequency detuning between the two semiconductor lasers. Furthermore, the comb spacing of the MFCs can be made tunable by varying the modulation frequency and selecting the matched operating parameters to adapt to different application scenarios. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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7 pages, 1873 KiB

Open AccessCommunication

Compact Diode-Pumped 946 nm Nd:YAG Laser with Good Beam Quality

by Rubel C. Talukder and Arkady Major

Photonics 2024, 11(2), 171; https://doi.org/10.3390/photonics11020171 - 12 Feb 2024

Viewed by 1797

Abstract

A continuous-wave (CW), high-power, quasi-three-level Nd:YAG laser operating at 946 nm is reported. The beam quality of the laser is greatly improved. The laser consists of a composite Nd:YAG rod end pumped by a fiber-coupled diode laser inside a simple concave-plane cavity. At [...] Read more.

A continuous-wave (CW), high-power, quasi-three-level Nd:YAG laser operating at 946 nm is reported. The beam quality of the laser is greatly improved. The laser consists of a composite Nd:YAG rod end pumped by a fiber-coupled diode laser inside a simple concave-plane cavity. At an incident pump power of 31 W, a maximum CW output of 9.98 W was obtained at 946 nm, with a beam quality factor of M²~5. The corresponding optical-to-optical efficiency was 32.2% with respect to the incident pump power. To the best of our knowledge, this is the highest output power at 946 nm with such a beam quality ever generated by diode-pumped Nd:YAG laser with bulk crystals. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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15 pages, 8180 KiB

Open AccessArticle

Thin and Large Depth-Of-Field Compound-Eye Imaging for Close-Up Photography

by Dewen Cheng, Da Wang, Cheng Yao, Yue Liu, Xilong Dai and Yongtian Wang

Photonics 2024, 11(2), 107; https://doi.org/10.3390/photonics11020107 - 25 Jan 2024

Cited by 1 | Viewed by 1593

Abstract

Large depth of field (DOF) and stereo photography are challenging yet rewarding areas of research in close-up photography. In this study, a compound-eye imaging system based on a discrete microlens array (MLA) was implemented for close-range thin imaging. A compact imaging system with [...] Read more.

Large depth of field (DOF) and stereo photography are challenging yet rewarding areas of research in close-up photography. In this study, a compound-eye imaging system based on a discrete microlens array (MLA) was implemented for close-range thin imaging. A compact imaging system with a total length of 3.5 mm and a DOF of 7 mm was realized using two planar aspherical MLAs in a hexagonal arrangement. A new three-layer structure and discrete arrangement of sublenses were proposed to suppress stray light and enable the spatial refocusing method, which restores image information at different object depths. The system is successfully fabricated, and the system performance is carefully investigated. Our system offers a large depth of field, high resolution, and portability, making it ideal for close-up photography applications requiring a short conjugate distance and small device volume, while also addressing the issue of crosstalk between adjacent channels. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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14 pages, 5023 KiB

Open AccessArticle

Evolution of Airy Beams in Turbulence Plasma Sheath

by Xuan Gao, Yiping Han, Jiajie Wang and Shuping Xu

Photonics 2024, 11(2), 102; https://doi.org/10.3390/photonics11020102 - 23 Jan 2024

Viewed by 1092

Abstract

In order to study the transmission characteristics of Airy beams in the plasma sheath, the flow field around a hypersonic vehicle was numerically simulated and analyzed based on the Navier–Stokes (N-S) equation and a turbulence model. Then, according to the characteristics of the [...] Read more.

In order to study the transmission characteristics of Airy beams in the plasma sheath, the flow field around a hypersonic vehicle was numerically simulated and analyzed based on the Navier–Stokes (N-S) equation and a turbulence model. Then, according to the characteristics of the thickness of the plasma flow field around the supersonic vehicle at the centimeter level, the double fast Fourier transform (D-FFT) algorithm and multi-random phase screens theory were used to predict the propagation characteristics of the Airy beams in the turbulent plasma sheath. The results show that the lower the height and the higher the speed, the smaller the thickness of the plasma sheath shock layer. The refractive index variation in the sheath shock layer has a significant influence on Airy beam transmission. At the same time, the transmission distance and the attenuation factor of the Airy beams also change the transmission quality of the Airy beams. The larger the attenuation factor, the smaller the drift, and the standard deviation decreases with an increase in the refractive index. Airy beams have smaller drifts compared to Gaussian beams and have advantages in suppressing turbulence. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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15 pages, 5189 KiB

Open AccessArticle

Investigation of Laser-Induced Cavity and Plasma Formation in Water Using Double-Pulse LIBS

by Michelle Siemens, Benjamin Emde, Marion Henkel, Ralf Methling, Steffen Franke, Diego Gonzalez and Jörg Hermsdorf

Physics 2024, 6(1), 108-122; https://doi.org/10.3390/physics6010008 - 12 Jan 2024

Cited by 2 | Viewed by 1245

Abstract

This paper deals with double-pulse laser-induced breakdown spectroscopy (LIBS) underwater, which is a promising analytical method for elemental analysis in the deep sea up to a water depth of 6000 m. A double-pulse laser with a wavelength of 1064 nm is used, which [...] Read more.

This paper deals with double-pulse laser-induced breakdown spectroscopy (LIBS) underwater, which is a promising analytical method for elemental analysis in the deep sea up to a water depth of 6000 m. A double-pulse laser with a wavelength of 1064 nm is used, which provides a pulse energy of up to 266 mJ for each laser pulse (in single pulse mode), a pulse width of 5–7 ns and a pulse delay in the range of 0.5 to 20 µs. In the double-pulse LIBS method, the first laser pulse creates a cavity on the material surface, and then the second laser pulse forms the plasma in this cavity. It is expected that the plasma is affected by the cavity’s size and lifetime. For this reason, the influence of focus position, pulse energy and pulse delay on the cavity and plasma formation at shallow water depth has been investigated. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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16 pages, 1712 KiB

Open AccessReview

Methods of Radiation Wavelength Tuning in Short-Pulsed Fibre Lasers

by Sergey Kobtsev

Photonics 2024, 11(1), 28; https://doi.org/10.3390/photonics11010028 - 28 Dec 2023

Cited by 2 | Viewed by 1406

Abstract

Methods of output wavelength tuning in short-pulsed fibre lasers are analysed. Many of them rely on spectral selection principles long used in other types of lasers. For compatibility with the fibre-optical format, the corresponding elements are sealed in compact, airtight volumes with fibre-optical [...] Read more.

Methods of output wavelength tuning in short-pulsed fibre lasers are analysed. Many of them rely on spectral selection principles long used in other types of lasers. For compatibility with the fibre-optical format, the corresponding elements are sealed in compact, airtight volumes with fibre-optical radiation input and output. A conclusion is presented about the relatively small number of inherently “fibre-optical” ways of tuning the wavelength of radiation. It is demonstrated that the range of output wavelength tuning in short-pulsed fibre lasers may span hundreds of nanometres (even without extension beyond the active medium gain contour through nonlinear effects). From the presented review results, it may be concluded that the search for the optimal tuning method complying with the user-preferred all-PM-fibre short-pulsed laser design is not yet complete. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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10 pages, 863 KiB

Open AccessCommunication

A Parabolic Waveform Generator Based on the Chirp Characteristics of a Directly Modulated Laser

by Na Chen, Yang Jiang, Xiaohong Lan, Yuejiao Zi, Jing Xu, Jiahui Li, Qiong Zhang and Jinjian Feng

Photonics 2024, 11(1), 4; https://doi.org/10.3390/photonics11010004 - 21 Dec 2023

Cited by 1 | Viewed by 1273

Abstract

Due to carrier dynamics, the modulated light field from a directly modulated laser (DML) has an intensity envelope with a certain frequency chirp. When the chirp is linearly mapped into intensity by a frequency discriminator such as an optical filter with a linear [...] Read more.

Due to carrier dynamics, the modulated light field from a directly modulated laser (DML) has an intensity envelope with a certain frequency chirp. When the chirp is linearly mapped into intensity by a frequency discriminator such as an optical filter with a linear edge, the optical field presents a new signal determined by the multiplication operation between the envelope function and the chirp function. Under a triangular drive signal, this process can contribute dark, bright and frequency-doubled bright parabolic waveforms by properly adjusting the filter window. This method is verified by both a theoretical analysis and experimental demonstrations. It not only provides a low-cost and simple scheme to generate parabola signals, but also a new method for arbitrary waveform generation. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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16 pages, 4408 KiB

Open AccessArticle

Simulation Test of The Aerodynamic Environment of A Missile-Borne Pulsed Laser Forward Detection System at High Flight Speed

by Peng Liu, Jian Li, Tuan Hua and He Zhang

Photonics 2023, 10(12), 1363; https://doi.org/10.3390/photonics10121363 - 10 Dec 2023

Viewed by 1373

Abstract

When a missile-borne pulsed laser forward detection system flies at supersonic speed, the laser beam will be distorted by the uneven outflow field, resulting in a significant reduction in ranging accuracy. In this paper, the impact of high flight speed on a pulsed [...] Read more.

When a missile-borne pulsed laser forward detection system flies at supersonic speed, the laser beam will be distorted by the uneven outflow field, resulting in a significant reduction in ranging accuracy. In this paper, the impact of high flight speed on a pulsed laser detection system is studied. First, a new ray tracing method with adaptive step size adjustment is proposed, which greatly improves the computational efficiency. Second, the aerodynamic environment of a munition flying at high speed is simulated by an intermittent transonic and supersonic wind tunnel to obtain the schlieren data of the flow field at various Mach numbers. The schlieren data present a shock wave structure similar to that of the simulation. In addition, the variation patterns of the pulsed laser echo waveform of the model under different aerodynamic conditions are studied to evaluate the detectability and operational stability of the laser detection system under static conditions. The test results match the simulation results well, and the two offer relatively consistent shock wave structures, which verifies the correctness and effectiveness of the flow field simulation model. The test echo waveforms are in good agreement with the simulated echo waveforms; the relative errors between the peak values of test and simulated echo waveforms at various Mach numbers do not exceed 20%, and the correlation coefficients between the test and simulated echo waveforms all exceed 0.7, indicating high correlations between the two. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 3125 KiB

Open AccessArticle

Acousto-Optic Transfer Function Control by a Phased-Array Piezoelectric Transducer

by Konstantin B. Yushkov, Alexander I. Chizhikov and Vladimir Ya. Molchanov

Photonics 2023, 10(10), 1167; https://doi.org/10.3390/photonics10101167 - 19 Oct 2023

Cited by 2 | Viewed by 1397

Abstract

We present analysis and numerical simulations of the acousto-optic spatial filter (AOSF) transfer function under the condition of dual-transducer operation and phase control. Based on these simulations, the AOSF crystal configuration is optimized for operation in the near-infrared wavelength region from 0.7 to [...] Read more.

We present analysis and numerical simulations of the acousto-optic spatial filter (AOSF) transfer function under the condition of dual-transducer operation and phase control. Based on these simulations, the AOSF crystal configuration is optimized for operation in the near-infrared wavelength region from 0.7 to 1.0

μ

m. We demonstrate that ultrasonic phase control can provide efficient tuning of the transfer function, which is independent of conventional frequency control. Thus, the application of phase control coupled with frequency control can reduce the transfer function asymmetry that is inherent to anisotropic Bragg diffraction in uniaxial crystals. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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14 pages, 4423 KiB

Open AccessArticle

Quantitative Evaluation of Biomechanical Properties of the Tongue Using a Shaker-Based Optical Coherence Elastography System

by Yubao Zhang, Jiahui Luo, Xiao Han, Gang Shi, Qin Zhang and Xingdao He

Photonics 2023, 10(10), 1143; https://doi.org/10.3390/photonics10101143 - 12 Oct 2023

Cited by 1 | Viewed by 1139

Abstract

Biomechanical properties of the tongue play a significant role in maintaining its normal physiological state. Although some techniques have been used to evaluate the tongue’s elasticity, they are limited in clinical detection because of low-resolution and invasive injuries. Here, a shaker-based optical coherence [...] Read more.

Biomechanical properties of the tongue play a significant role in maintaining its normal physiological state. Although some techniques have been used to evaluate the tongue’s elasticity, they are limited in clinical detection because of low-resolution and invasive injuries. Here, a shaker-based optical coherence elastography technique that possesses features of high resolution, high sensitivity, and non-destructive imaging was designed and applied to the elastic detection of the tongue for the first time. Repeated experiments were conducted on the in vivo beagle tongue whose shear modulus and Young’s modulus were quantified by visualization of the shear wave propagation, which indicates that our technique is reliable and operable, and may be potentially utilized in clinical fields with further refinement. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 3316 KiB

Open AccessArticle

Spot Invalid Point Repair Algorithm of Detector Array Measurement System Based on Image Correlation Coefficient

by Yilun Cheng, Gangyu Wang, Fengfu Tan, Feng He, Laian Qin, Zhigang Huang and Zaihong Hou

Photonics 2023, 10(10), 1105; https://doi.org/10.3390/photonics10101105 - 30 Sep 2023

Viewed by 1021

Abstract

The detector array method has been widely used in the field of high-energy laser far-field spot parameter measurement due to its ability to directly measure the far-field spot of high-energy lasers, wide dynamic range of the detectors, high system sampling frequency, good real-time [...] Read more.

The detector array method has been widely used in the field of high-energy laser far-field spot parameter measurement due to its ability to directly measure the far-field spot of high-energy lasers, wide dynamic range of the detectors, high system sampling frequency, good real-time performance, and suitability for various testing environment requirements. However, during the measurement process, the irradiation of strong lasers or damage to other hardware systems can result in invalid points in the acquired spot images, thereby reducing the measurement accuracy of the system. In order to achieve accurate measurement of laser far-field spot parameters, this paper establishes an experimental model based on the analysis of the sampling spacing of the detector array target and proposes a laser far-field spot invalid point repair algorithm based on image correlation coefficient. Experimental results demonstrate that the algorithm proposed in this paper effectively reduces the impact of invalid points in the measurement system on the measurement accuracy, and achieves accurate measurement of high-energy laser measurement systems. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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13 pages, 4538 KiB

Open AccessArticle

Bidirectional Atmospheric Channel Reciprocity-Based Adaptive Power Transmission

by Wenyao Liu, Xuehen Chen, Miao Liu and Yanqing Hong

Photonics 2023, 10(10), 1067; https://doi.org/10.3390/photonics10101067 - 22 Sep 2023

Cited by 1 | Viewed by 1074

Abstract

In atmosphere free-space optical communication (FSO) systems, the scintillation effect produced by turbulence effects increases the bit error rate (BER) of the communication system and reduces the system’s performance. However, a high correlation of turbulent noise occurs in the two transmission channels when [...] Read more.

In atmosphere free-space optical communication (FSO) systems, the scintillation effect produced by turbulence effects increases the bit error rate (BER) of the communication system and reduces the system’s performance. However, a high correlation of turbulent noise occurs in the two transmission channels when a signal transmitted in the bidirectional atmospheric channel with channel reciprocity. The performance of the FSO system can be increased by extracting channel state information (CSI) in forward transmission and using adaptive power technology to reduce turbulence in inverse transmission. In this research, we propose a bidirectional atmospheric channel reciprocity-based adaptive power transmission (CR-APT) technique that lowers the bit error rate of the transmitted signal by using the CSI of the relevant channel. To verify the effectiveness of the technique, a bidirectional atmospheric channel with various turbulence intensities is built in the simulation program, along with various background sounds to vary the channel reciprocity, and the impact of reciprocity on signal transmission is examined. The simulation findings demonstrate that adaptive power transmission with high reciprocity is excellent under the weak turbulence condition, and its future development is promising. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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9 pages, 1035 KiB

Open AccessCommunication

The Degradation of Antibiotics by Reactive Species Generated from Multi-Gas Plasma Jet Irradiation

by Yu-ki Tanaka, Taiki Osawa, Yoshikazu Yamagishi, Akitoshi Okino and Yasumitsu Ogra

Plasma 2023, 6(3), 541-549; https://doi.org/10.3390/plasma6030037 - 4 Sep 2023

Viewed by 1727

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) often causes serious infections in hospitals. Vancomycin is widely accepted as the standard therapy for MRSA infection, but its widespread use has resulted in the generation of vancomycin-resistant S. aureus (VRSA). To reduce the potential risk of MRSA and [...] Read more.

Methicillin-resistant Staphylococcus aureus (MRSA) often causes serious infections in hospitals. Vancomycin is widely accepted as the standard therapy for MRSA infection, but its widespread use has resulted in the generation of vancomycin-resistant S. aureus (VRSA). To reduce the potential risk of MRSA and VRSA emergence in aquatic environments, we investigated the degradation of methicillin and vancomycin by cold atmospheric pressure plasma jet (APPJ) irradiation using N₂, O₂, and CO₂ gases. The concentrations of methicillin and vancomycin in distilled water were decreased in a time-dependent manner by the plasma jet irradiation; that is, compared with the pre-treatment levels, the concentrations of methicillin and vancomycin were reduced by 20 to 50% after plasma jet irradiation for 10 s. No methicillin and vancomycin signals were detected after 300 s irradiation. Reactive species generated from the plasma jet electrophilically attacked and fragmented the antibiotic molecules. The present method realizes direct plasma ignition in a solution, and therefore, the reactive species can easily react with antibiotic molecules. In addition, plasma can be generated from various gas species that are abundant in the atmosphere. Therefore, cold APPJ irradiation can be a powerful, cost-effective, and environmentally friendly means for the treatment of antibiotics in aqueous samples. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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16 pages, 2701 KiB

Open AccessArticle

Enhanced XUV Harmonics Generation with an Intense Laser Field in the Overdriven Regime

by Zhiyong Qin, Zibo Xu, Changhai Yu, Jiansheng Liu, Jintan Cai, Zhijun Zhang, Shiyi Zhou, Xuhui Jiao and Zhongtao Xiang

Photonics 2023, 10(9), 964; https://doi.org/10.3390/photonics10090964 - 23 Aug 2023

Cited by 1 | Viewed by 1277

Abstract

High-order harmonic generation with high photon flux has been a challenging task in strong-field physics. According to the high-order harmonic generation process, the essential requirements for achieving efficient harmonic radiations inside a gas medium are the improvement of the induced atomic dipole moment [...] Read more.

High-order harmonic generation with high photon flux has been a challenging task in strong-field physics. According to the high-order harmonic generation process, the essential requirements for achieving efficient harmonic radiations inside a gas medium are the improvement of the induced atomic dipole moment amplitude of the single-atom response in the microscopic and the phase matching of the high harmonics in the macroscopic medium. In this work, we demonstrated a feasible approach to enhance the extreme-ultraviolet harmonics in the plateau region by increasing the intensity of the driving laser while keeping the laser energy constant. The simulation results showed that by increasing the laser intensity to the overdriven regime, the average extreme-ultraviolet harmonics yield in the plateau region is approximately twice as high as that obtained optimally in the conventional loose focusing geometry scheme by utilizing a relatively low-intensity driving laser with the same laser energy. The quantitative analysis of the harmonics generation process in the macroscopic medium and the phase matching revealed that the observed enhancement in harmonics can be attributed to the amplification of the induced atomic dipole moment amplitude of the single-atom response in the high-intensity driving laser and the favorable transient phase matching in the overdriven regime. Furthermore, the investigation of the driving laser indicated that the favorable transient phase matching is caused by the spatiotemporal reshaping of the driving laser in the overdriven regime. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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18 pages, 31481 KiB

Open AccessArticle

The Transport and Optical Characteristics of a Metal Exposed to High-Density Energy Fluxes in Compressed and Expanded States of Matter

by Nikolay B. Volkov and Alexander I. Lipchak

Condens. Matter 2023, 8(3), 70; https://doi.org/10.3390/condmat8030070 - 11 Aug 2023

Cited by 1 | Viewed by 1508

Abstract

This article presents a theoretical study of the optical and transport properties of metals. Iron, as an example, was used to discuss, through a theoretical description, the peculiarities of these properties in the compressed and expanded states under the influence of high-density energy [...] Read more.

This article presents a theoretical study of the optical and transport properties of metals. Iron, as an example, was used to discuss, through a theoretical description, the peculiarities of these properties in the compressed and expanded states under the influence of high-density energy fluxes. By solving the semi-classical Boltzmann equation for conduction electrons for a broad range of densities and temperatures, the expressions of electrical conductivity, electronic thermal conductivity, and thermoelectric coefficient calculations were derived. The real and imaginary parts of the iron permittivity and the energy absorption coefficient for the first and second harmonics of Nd:YAG laser radiation were obtained. The calculation peculiarities of the metal’s optical characteristics of matter in an expanded state in a broad range of densities and temperatures were considered. The analysis of the obtained results shows their agreement with the theoretical description for cases of ideal non-degenerate and dense degenerate electron plasmas. It is shown that the behavior of the electrical conductivity and optical characteristics in the critical and supercritical regions of density and temperature are in agreement with the known experimental results. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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19 pages, 5900 KiB

Open AccessEditor’s ChoiceArticle

Optical Trapping of Chiral Particles by Dual Laser Beams

by Jing Bai, Cheng-Xian Ge and Zhen-Sen Wu

Photonics 2023, 10(8), 905; https://doi.org/10.3390/photonics10080905 - 4 Aug 2023

Cited by 4 | Viewed by 1784

Abstract

In this paper, an analytical method for studying the radiation force (RF) of chiral spheres generated by dual laser beams is presented under the framework of generalized Lorenz–Mie theory (GLMT). According to the coordinate transformation relations, the arbitrarily incident laser beam is represented [...] Read more.

In this paper, an analytical method for studying the radiation force (RF) of chiral spheres generated by dual laser beams is presented under the framework of generalized Lorenz–Mie theory (GLMT). According to the coordinate transformation relations, the arbitrarily incident laser beam is represented by vector spherical harmonic functions (VSHFs) in the sphere system. The entire induced field expression coefficients of dual laser beams can be obtained by superposition of each illuminated field. Based on the momentum conservation theory, the concrete expression of lateral and axial RF on chiral sphere is derived. The current theories are shown to be valid by comparison with the existing reference. To investigate the stable capture state of chiral sphere, the influences of the corresponding parameters of chiral particles and dual laser beams on the trapping and manipulation are investigated in detail. The analytical study on the RF of dual laser beams on chiral particles is an efficient method for improving optical tweezers technology and can become an encouraging approach to realize the high accuracy operation of chiral particles. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 2979 KiB

Open AccessCommunication

Optimization of Longitudinal Alignment of an 4f System in a Compact Vectorial Optical-Field Generator Based on a High-Resolution Liquid Crystal Spatial Light Modulator

by Mingyu Li and Yuanzheng Liu

Photonics 2023, 10(8), 894; https://doi.org/10.3390/photonics10080894 - 2 Aug 2023

Viewed by 1705

Abstract

Vectorial optical fields have garnered significant attention due to their potential applications in areas such as optical nano-fabrication, optical micromachining, quantum information processing, optical imaging, and so on. Traditional compact vectorial optical generators with amplitude modulation perform poorly in terms of diffraction effect [...] Read more.

Vectorial optical fields have garnered significant attention due to their potential applications in areas such as optical nano-fabrication, optical micromachining, quantum information processing, optical imaging, and so on. Traditional compact vectorial optical generators with amplitude modulation perform poorly in terms of diffraction effect reduction. To tackle this problem, the refractive 4f system in amplitude modulation is longitudinally aligned using an optimization approach presented in this research. The phase images used for longitudinal alignment are loaded into the liquid crystal spatial light modulator (SLM), and the distance between the lens and the mirror in the reflective 4f system is adjusted for longitudinal alignment by compensating for the neglected phase in the integrated module for the compact vectorial optical-field generator. The spot images collected by the CCD are processed using the improved eight-direction Sobel operator and Roberts function, and the longitudinal alignment in the reflective 4f system is determined by the sharpness of the image. The sharpness of the edges of the lines and the overall image are both enhanced after optimization compared to before optimization. The results demonstrate that the proposed method can effectively reduce the longitudinal alignment error of the reflective 4f system in the amplitude modulation of the compact vectorial optical-field generator, lessen the diffraction effect, and improve the performance of the system. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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15 pages, 6033 KiB

Open AccessArticle

Influence of Image Processing Method on Wavefront Reconstruction Accuracy of Large-Aperture Laser

by Gangyu Wang, Zaihong Hou, Laian Qin, Xu Jing, Yang Li and Yi Wu

Photonics 2023, 10(7), 799; https://doi.org/10.3390/photonics10070799 - 10 Jul 2023

Viewed by 1068

Abstract

In order to improve the wavefront reconstruction accuracy of a large-aperture laser, this paper proposed an adaptive window preprocessing algorithm based on the threshold center of gravity method (AW-TCoG). The effects of median filtering and mean filtering on spot image processing and wavefront [...] Read more.

In order to improve the wavefront reconstruction accuracy of a large-aperture laser, this paper proposed an adaptive window preprocessing algorithm based on the threshold center of gravity method (AW-TCoG). The effects of median filtering and mean filtering on spot image processing and wavefront reconstruction accuracy are simulated and analyzed. The results show that the mean filtering method has a better effect on noise elimination and can further improve the accuracy of wavefront reconstruction. In addition, the centroid detection errors of large-aperture laser wavefront reconstruction through the center of gravity (CoG), the threshold center of gravity (T-CoG), and the Windowing method were studied. The analysis shows that, due to the influence of noise, the wavefront reconstruction accuracy is poor when the CoG and Windowing methods are used to calculate centroid parameters, while the wavefront reconstruction accuracy of the threshold centroid method is better and can reach 0.2λ. When using the AW-TCoG proposed in this paper, the wavefront reconstruction accuracy can be maintained within 0.1λ for different incident wavefront RMS values and spot images with different signal-to-noise ratio (SNR) levels. Compared with the traditional threshold centroid method, the wavefront reconstruction accuracy of this method is significantly improved. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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9 pages, 3140 KiB

Open AccessCommunication

Generation of Flat Terahertz Noise by Mixing Incoherent Light Fields

by Youwen Zhang, Wenjie Liu, Ya Guo, Junbin Liu, Zhiwei Jia, Yuehui Sun, Anbang Wang and Yuncai Wang

Photonics 2023, 10(7), 778; https://doi.org/10.3390/photonics10070778 - 4 Jul 2023

Cited by 2 | Viewed by 1237

Abstract

Terahertz (THz) noise sources play an irreplaceable role in testing THz devices and evaluating THz application systems, and the flatness of their radio frequency (RF) spectra is an important technical parameter. In this paper, a scheme for generating flat THz noise by mixing [...] Read more.

Terahertz (THz) noise sources play an irreplaceable role in testing THz devices and evaluating THz application systems, and the flatness of their radio frequency (RF) spectra is an important technical parameter. In this paper, a scheme for generating flat THz noise by mixing multiple filtered incoherent light fields is proposed. A theoretical analysis is conducted to investigate the impact of different spectral linewidths and central wavelength differences of incoherent light fields on the noise power and RF spectrum flatness, and an optimized experimental scheme is obtained. The results show that the proposed method can generate a 280–380 GHz flat THz noise signal with an RF spectrum flatness of ±0.5 dB in simulation and ±2.7 dB in our experiments. This article provides an excellent technical solution to the demand for flat THz noise in the THz field. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 3374 KiB

Open AccessCommunication

Tunable Multiple Surface Plasmonic Bending Beams into Single One by Changing Incident Light Wavelength

by Hang Zhang, Liang Wang, Xueli Li, Xiaoming Li and Hui Li

Photonics 2023, 10(7), 758; https://doi.org/10.3390/photonics10070758 - 30 Jun 2023

Cited by 1 | Viewed by 1154

Abstract

Controllable surface plasmonic bending beams (SPBs) with propagating along bending curves have a wide range of applications in the fields of fiber sensors, optical trapping, and micro-nano manipulations. In terms of designing and optimizing controllable SPB generators, there is great significance in realizing [...] Read more.

Controllable surface plasmonic bending beams (SPBs) with propagating along bending curves have a wide range of applications in the fields of fiber sensors, optical trapping, and micro-nano manipulations. In terms of designing and optimizing controllable SPB generators, there is great significance in realizing conversion between multiple SPBs and single SPB without rebuilding metasurface structures. In this study, a SPB generator, composed of an X-shaped nanohole array, is proposed to realize conversion between multiple SPBs and a single one by changing the incident light wavelength. The Fabry–Pérot (F–P) resonance effect of SPPs in nanoholes and localized surface plasmonic (LSP) resonance of the nanohole are utilized to explain this conversion. It turns out that the relationship between the electric field intensities of SPBs and the polarization angle of incident light satisfies the sine distribution, which is consistent with dipole radiation theory. In addition, we also find that the electric field intensities of SPBs rely on the width, length, and angle of the X-shaped nanohole. These findings could help in designing and optimizing controllable and multi-functions SPBs converters. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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10 pages, 8592 KiB

Open AccessCommunication

Determining Single Photon Quantum States through Robust Waveguides on Chip

by Gustavo Armendáriz and Víctor Velázquez

Photonics 2023, 10(7), 755; https://doi.org/10.3390/photonics10070755 - 30 Jun 2023

Cited by 1 | Viewed by 1034

Abstract

Waveguided beam splitters were microfabricated by using a commercial two-photon lithography system (Nanoscribe), Ip-Dip as the waveguides and fused silica as the substrate, and they were covered with Loctite. The gap between the waveguides in the coupler was used to determine the transmission [...] Read more.

Waveguided beam splitters were microfabricated by using a commercial two-photon lithography system (Nanoscribe), Ip-Dip as the waveguides and fused silica as the substrate, and they were covered with Loctite. The gap between the waveguides in the coupler was used to determine the transmission and reflection coefficients, and our results were compared with simulation results (using OptiFDTD software). The input and output ports of the beam splitters were spliced with multimode optical fibers in a robust system that can easily be handled. Then, they were tested by leading single photons (from an SPDC) to the beam splitters to produce different quantum statistics that were rated using the Fano factor. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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7 pages, 2758 KiB

Open AccessCommunication

210-W, Quasi-Continuous Wave, Nd:YAG InnoSlab Laser at 1319 nm

by Xiangrui Meng, Xingwang Luo, Junzhi Ye, Xiaoming Chen, Xuguang Zhang, Lei Zhang, Qingsong Gao and Baole Lu

Photonics 2023, 10(7), 730; https://doi.org/10.3390/photonics10070730 - 26 Jun 2023

Viewed by 1364

Abstract

In this paper, we demonstrate a high-power, quasi-continuous wave using a laser-diode dual-end-pumped Nd:YAG InnoSlab laser at 1319 nm. The maximum average output power of 210 W at a single 1319 nm wavelength is obtained with an optical-optical efficiency of 18.8% from absorbed [...] Read more.

In this paper, we demonstrate a high-power, quasi-continuous wave using a laser-diode dual-end-pumped Nd:YAG InnoSlab laser at 1319 nm. The maximum average output power of 210 W at a single 1319 nm wavelength is obtained with an optical-optical efficiency of 18.8% from absorbed pump power to laser output. The output pulse duration is 246 μs at the repetition of 500 Hz, and the beam quality factors of M² are 1.37 and 1.47 in the horizontal and vertical directions, respectively. This is the first report on high-power, quasi-continuous wave using Nd:YAG InnoSlab lasers at 1319 nm with good beam quality. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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8 pages, 993 KiB

Open AccessCommunication

Dynamic Tunable Deflection of Radiation Based on Epsilon-Near-Zero Material

by Lin Cheng, Kun Huang, Yu Wang and Fan Wu

Photonics 2023, 10(6), 688; https://doi.org/10.3390/photonics10060688 - 14 Jun 2023

Cited by 1 | Viewed by 1251

Abstract

Epsilon-near-zero nanoantennas can be used to tune the far-field radiation pattern due to their exceptionally large intensity-dependent refractive index. In this study, we propose a hybrid optical antenna based on indium tin oxide (ITO) to enable optical tuning of the deflection of radiation, [...] Read more.

Epsilon-near-zero nanoantennas can be used to tune the far-field radiation pattern due to their exceptionally large intensity-dependent refractive index. In this study, we propose a hybrid optical antenna based on indium tin oxide (ITO) to enable optical tuning of the deflection of radiation, specifically a hybrid structure antenna of ITO and dielectric material, which makes the deflection angle changes 17

^{\circ}

as incident intensities increase. Moreover, by employing an array of ITO or hybrid nanodisks, we can enhance the unidirectionality of the radiation pattern, resulting in a needle-like shape with an angular beam width

α <

8

^{\circ}

of the main lobe. The deflection angle of the radiation pattern response with the needle-like lobe paves the way for further studies and applications in beam steering and optical modulation where dynamic control of the nanoantennas is highly desirable. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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7 pages, 2471 KiB

Open AccessCommunication

Hybrid Resonator 1319 nm Nd:YAG InnoSlab Laser

by Shengzi Zhang, Tanghan Chen, Xiaomeng Liu, Hengli Zhang, Jiang Wang and Heqing Guo

Photonics 2023, 10(6), 652; https://doi.org/10.3390/photonics10060652 - 5 Jun 2023

Viewed by 1628

Abstract

The InnoSlab laser has the advantages of excellent thermal management and high overlapping efficiency. In this work, we report an InnoSlab laser with high efficiency at 1319 nm end-pumped 0.6at.% Nd:YAG by 808 nm. The hybrid stable–unstable resonator was adopted. For a cavity [...] Read more.

The InnoSlab laser has the advantages of excellent thermal management and high overlapping efficiency. In this work, we report an InnoSlab laser with high efficiency at 1319 nm end-pumped 0.6at.% Nd:YAG by 808 nm. The hybrid stable–unstable resonator was adopted. For a cavity length of 17.9 mm and absorbed pumped power of 423.5 W, the output power of 81 W was obtained at T = 5%, exhibiting an optical conversion efficiency of 19.13% and a slope efficiency of 29.80%. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 4194 KiB

Open AccessArticle

Plasma Treatment of Polystyrene Films—Effect on Wettability and Surface Interactions with Au Nanoparticles

by Mohammad Islam, Zineb Matouk, Nadir Ouldhamadouche, Jean-Jacques Pireaux and Amine Achour

Plasma 2023, 6(2), 322-333; https://doi.org/10.3390/plasma6020022 - 29 May 2023

Cited by 4 | Viewed by 2496

Abstract

Polystyrene (PS)/Gold (Au) is used for a wide range of applications, including composite nanofibers, catalysis, organic memory devices, and biosensing. In this work, PS films were deposited on silicon substrates via a spin coating technique followed by treatment with argon (Ar) plasma admixed [...] Read more.

Polystyrene (PS)/Gold (Au) is used for a wide range of applications, including composite nanofibers, catalysis, organic memory devices, and biosensing. In this work, PS films were deposited on silicon substrates via a spin coating technique followed by treatment with argon (Ar) plasma admixed with ammonia (NH₃), oxygen (O₂), or tetrafluoroethane (C₂H₂F₄). X-Ray photoelectron spectroscopy (XPS) analysis revealed modified surface chemistry for Ar/O₂, Ar/NH₃, or Ar/C₂H₂F₄ plasma treatment through the incorporation of oxygen, nitrogen, or fluorine groups, respectively. Size-controlled magnetron sputter deposition of Au nanoparticles (NP) onto these plasma-treated PS films was investigated via XPS and AFM techniques. The interaction of the Au NPs, as probed from the XPS and AFM measurements, is discussed by referring to changes in surface chemistry and morphology of the PS after plasma treatment. The results demonstrate the effect of surface chemistry on the interaction of Au NPs with polymer support having different surface functionalities. The XPS results show that significant oxygen surface incorporation resulted from oxygen-containing species in the plasma itself. The surface concentration of O increased from 0.4% for the pristine PS to 4.5 at%, 35.4 at%, and 45.6 at% for the Ar/C₂H₄F₄, Ar/NH₃, and Ar/O₂, respectively. The water contact angle (WCA) values were noticed to decrease from 98° for the untreated PS to 95°, 37°, and 15° for Ar/C₂H₂F₄, Ar/NH₃, and Ar/O₂ plasma-modified PS samples, respectively. AFM results demonstrate that surface treatment was also accompanied by surface morphology change. Small Au islands are well dispersed and cover the surface, thus forming a homogeneous, isotropic structure. The reported results are important for exploiting Au NPs use in catalysis and sensing applications. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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11 pages, 2902 KiB

Open AccessCommunication

Decryption of Deterministic Phase-Encoded Digital Holography Using Convolutional Neural Networks

by Huang-Tian Chan and Chi-Ching Chang

Photonics 2023, 10(6), 612; https://doi.org/10.3390/photonics10060612 - 25 May 2023

Cited by 1 | Viewed by 1276

Abstract

Digital holographic encryption is an important information security technology. Traditional encryption techniques require the use of keys to encrypt information. If the key is lost, it is difficult to recover information, so new technologies that allow legitimate authorized users to access information are [...] Read more.

Digital holographic encryption is an important information security technology. Traditional encryption techniques require the use of keys to encrypt information. If the key is lost, it is difficult to recover information, so new technologies that allow legitimate authorized users to access information are necessary. This study encrypts fingerprints and other data using a deterministic phase-encoded encryption system that uses digital holography (DPDH) and determines whether decryption is possible using a convolutional neural network (CNN) using the U-net model. The U-net is trained using a series of ciphertext-plaintext pairs. The results show that the U-net model decrypts and reconstructs images and that the proposed CNN defeats the encryption system. The corresponding plaintext (fingerprint) is retrieved from the ciphertext without using the key so that the proposed method performs well in terms of decryption. The proposed scheme simplifies the decryption process and can be used for information security risk assessment. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 5204 KiB

Open AccessCommunication

1064/1319 nm Dual-Wavelength Alternating Electro-Optic Q-Switched Laser Based on the Common Q-Switching Bias Voltage

by Jingdong Sun, Chunhe Yu, Yuan Dong, Chunting Wu and Guangyong Jin

Photonics 2023, 10(6), 609; https://doi.org/10.3390/photonics10060609 - 24 May 2023

Viewed by 1535

Abstract

A dual-wavelength alternating electro-optic (EO) Q-switched laser operating at 1064 and 1319 nm is designed, which takes the structure of double the gain crystals and a single EO modulator with the common Q-switching bias voltage (CQBV). The output characteristics of alternating dual-wavelength pulse [...] Read more.

A dual-wavelength alternating electro-optic (EO) Q-switched laser operating at 1064 and 1319 nm is designed, which takes the structure of double the gain crystals and a single EO modulator with the common Q-switching bias voltage (CQBV). The output characteristics of alternating dual-wavelength pulse lasers are studied via simulations and experiments. The results show that the energy ratio of the two lasing wavelengths can be controlled by changing the CQBV. This is because the CQBV affects the loss of two resonators, 1064 and 1319 nm, at the same time. The gain–loss relationship in the dual-wavelength laser resonators can be controlled by changing the CQBV in a certain range. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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13 pages, 4957 KiB

Open AccessArticle

Optical Engine Design for a Compact, High-Luminance DLP Projector Using Four-Channel LEDs and a Total Internal Reflection Prism

by Shuihai Peng, Zhiyao Zhang and Yong Liu

Photonics 2023, 10(5), 559; https://doi.org/10.3390/photonics10050559 - 11 May 2023

Viewed by 4525

Abstract

How to obtain higher brightness with a small volume projection engine for 4K resolution digital light processing (DLP) is of great significance. In this paper, we first use the fourth channel serving as a blue pump leading to a 52% gain of green [...] Read more.

How to obtain higher brightness with a small volume projection engine for 4K resolution digital light processing (DLP) is of great significance. In this paper, we first use the fourth channel serving as a blue pump leading to a 52% gain of green brightness. Secondly, a new inline total internal reflection prism glued with a spherical mirror is constructed to notably reduce the length of the relay illumination system by more than 10 mm, resulting in a more compact optical engine with a volume of 210 × 140 × 36 mm³. Thirdly, a projection lens is optimized with a modulation transfer function higher than 0.6 at 93 lines for a distance of 2125 mm with distortion lower than 1%. As a result, the efficiencies of RGB lights are higher than 60%, and the luminance and uniformity on the screen reach 1412 lm and 94.5% measured by the prototype. Our proposed projection system is significantly helpful for designing a compact and high-luminance 4K DLP projection. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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16 pages, 6251 KiB

Open AccessArticle

Preliminary Study on Automatic Detection of Hard Defects in Integrated Circuits Based on Thermal Laser Stimulation

by Wenjian Wu, Yingqi Ma, Minghui Cai and Jianwei Han

Photonics 2023, 10(5), 540; https://doi.org/10.3390/photonics10050540 - 6 May 2023

Viewed by 1567

Abstract

Locating the fault position is a crucial part of the failure mechanism analysis of integrated circuits. This paper proposes a hard defect locating system based on Thermal Laser Stimulation (TLS) technology. The equation for laser-induced changes in the electrical parameters of semiconductor devices [...] Read more.

Locating the fault position is a crucial part of the failure mechanism analysis of integrated circuits. This paper proposes a hard defect locating system based on Thermal Laser Stimulation (TLS) technology. The equation for laser-induced changes in the electrical parameters of semiconductor devices is a good guide to the hardware and software design of the hard defect locating system. The scanning mode of fast total scanning combined with slow point-to-point scanning can quickly locate abnormal areas. A modified median absolute difference (MAD) method is applied to the extraction of anomalous data. The system software can automatically and collaboratively control the 3D mobile station, laser, and signal acquisition unit. It also can intuitively display the distribution of abnormal points on the infrared image. Using a failure MRAM chip and a good one to conduct a comparative test, the abnormal points distributed on the infrared image of the chip indicate that the failure area is in the digital module or eFuse module of the chip, and the Emission Microscopy (EMMI) experiment also verifies the accuracy of the test system. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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13 pages, 3227 KiB

Open AccessArticle

Study on the Expansion Kinetics of Plasma and Absorption Wave Induced by Millisecond-Nanosecond Combined Pulse Lasers in Fused Quartz

by Congrui Geng, Jixing Cai, Yubo Liu, Zequn Zhang, Hongtao Mao, Hao Yu and Yunpeng Wang

Photonics 2023, 10(4), 411; https://doi.org/10.3390/photonics10040411 - 6 Apr 2023

Cited by 3 | Viewed by 1570

Abstract

The transient temperature field, the velocity and pressure of plasma, and the absorption wave of fused quartz induced by millisecond-nanosecond combined pulse lasers are simulated. The theoretical model of plasma and absorption wave produced by fused quartz irradiated by a millisecond-nanosecond pulsed laser [...] Read more.

The transient temperature field, the velocity and pressure of plasma, and the absorption wave of fused quartz induced by millisecond-nanosecond combined pulse lasers are simulated. The theoretical model of plasma and absorption wave produced by fused quartz irradiated by a millisecond-nanosecond pulsed laser is established, in which pulse delay and laser energy are essential variables. The results show that the damaged effect of the millisecond-nanosecond combined pulse laser is different under the damaged effect of different pulse delay conditions. When the energy densities of millisecond-nanosecond combined pulse lasers are 800 J/cm² and 20 J/cm², respectively, the range of pulse delay is 0 ms <

Δ t

≤ 3 ms, and the energy coupling efficiency is the highest when

Δ t

= 1 ms. The addition of a nanosecond pulsed laser causes more obvious thermal damage and optical breakdown to fused quartz. The high pressure is concentrated at the plasma expansion interface or the shock wave front. The results can optimize the simulation parameters and be applied to laser plasma processing technology. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 4494 KiB

Open AccessArticle

A Cylindrical Optical-Space Black Hole Induced from High-Pressure Acoustics in a Dense Fluid

by Edward A. Rietman, Brandon Melcher, Alexey Bobrick and Gianni Martire

Universe 2023, 9(4), 162; https://doi.org/10.3390/universe9040162 - 28 Mar 2023

Cited by 2 | Viewed by 6233

Abstract

We describe the construction of an optical-space, cylindrical black hole induced by high pressure in a dense fluid. Using an approximate analogy between curved spacetime and optics in moving dielectric media, we derive the mass of the black hole thus created. We describe [...] Read more.

We describe the construction of an optical-space, cylindrical black hole induced by high pressure in a dense fluid. Using an approximate analogy between curved spacetime and optics in moving dielectric media, we derive the mass of the black hole thus created. We describe the resulting optical-space using a Bessel beam profile and Snell’s law to understand how total internal reflection produces a cylindrical, optic black hole. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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7 pages, 2278 KiB

Open AccessCommunication

Feasibility Demonstration of THz Wave Generation/Modulation Based on Photomixing Using a Single Wavelength-Tunable Laser

by Takashi Shiramizu, Naoya Seiki, Ryo Matsumoto, Naoto Masutomi, Yuya Mikami, Yuta Ueda and Kazutoshi Kato

Photonics 2023, 10(4), 369; https://doi.org/10.3390/photonics10040369 - 25 Mar 2023

Cited by 4 | Viewed by 1589

Abstract

The photomixing of two lightwaves is one of the promising methods of generating a terahertz (THz) wave. The conventional photomixing system consisting of two lasers and a modulator results in large transmitter volumes and high power consumption. To solve this issue, we devised [...] Read more.

The photomixing of two lightwaves is one of the promising methods of generating a terahertz (THz) wave. The conventional photomixing system consisting of two lasers and a modulator results in large transmitter volumes and high power consumption. To solve this issue, we devised a novel THz wave generation and modulation system based on photomixing using a single wavelength-tunable laser in combination with delayed self-multiplexing. We successfully demonstrated the feasibility of 300-GHz wave generation and modulation. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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13 pages, 3179 KiB

Open AccessArticle

Multistage Positron Acceleration by an Electron Beam-Driven Strong Terahertz Radiation

by Jie Zhao, Yan-Ting Hu, Hao Zhang, Yu Lu, Li-Xiang Hu, Fu-Qiu Shao and Tong-Pu Yu

Photonics 2023, 10(4), 364; https://doi.org/10.3390/photonics10040364 - 24 Mar 2023

Cited by 3 | Viewed by 2031

Abstract

Laser–plasma accelerators (LPAs) have been demonstrated as one of the candidates for traditional accelerators and have attracted increasing attention due to their compact size, high acceleration gradients, low cost, etc. However, LPAs for positrons still face many challenges, such as the beam divergence [...] Read more.

Laser–plasma accelerators (LPAs) have been demonstrated as one of the candidates for traditional accelerators and have attracted increasing attention due to their compact size, high acceleration gradients, low cost, etc. However, LPAs for positrons still face many challenges, such as the beam divergence controlling, large energy spread, and complicated plasma backgrounds. Here, we propose a possible multistage positron acceleration scheme for high energy positron beam acceleration and propagation. It is driven by the strong coherent THz radiation generated when an injected electron ring beam passes through one or more solid targets. Multidimensional particle-in-cell simulations demonstrated that each acceleration stage is able to provide nearly 200 MeV energy gain for the positrons. Meanwhile, the positron beam energy spread can be controlled within 2%, and the beam emittance can be maintained during the beam acceleration and propagation. This may attract one’s interests in potential experiments on both large laser facilities and a traditional accelerator together with a laser system. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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13 pages, 9555 KiB

Open AccessArticle

Prediction of the Number of Cumulative Pulses Based on the Photon Statistical Entropy Evaluation in Photon-Counting LiDAR

by Mingwei Huang, Zijing Zhang, Longzhu Cen, Jiahuan Li, Jiaheng Xie and Yuan Zhao

Entropy 2023, 25(3), 522; https://doi.org/10.3390/e25030522 - 17 Mar 2023

Cited by 3 | Viewed by 1544

Abstract

Photon-counting LiDAR encounters interference from background noise in remote target detection, and the statistical detection of the accumulation of multiple pulses is necessary to eliminate the uncertainty of responses from the Geiger-mode avalanche photodiode (Gm-APD). The cumulative number of statistical detections is difficult [...] Read more.

Photon-counting LiDAR encounters interference from background noise in remote target detection, and the statistical detection of the accumulation of multiple pulses is necessary to eliminate the uncertainty of responses from the Geiger-mode avalanche photodiode (Gm-APD). The cumulative number of statistical detections is difficult to select due to the lack of effective evaluation of the influence of the background noise. In this work, a statistical detection signal evaluation method based on photon statistical entropy (PSE) is proposed by developing the detection process of the Gm-APD as an information transmission model. A prediction model for estimating the number of cumulative pulses required for high-accuracy ranging with the background noise is then established. The simulation analysis shows that the proposed PSE is more sensitive to the noise compared with the signal-to-noise ratio evaluation, and a minimum PSE exists to ensure all the range detections with background noise are close to the true range with a low and stable range error. The experiments demonstrate that the prediction model provides a reliable estimation of the number of required cumulative pulses in various noise conditions. With the estimated number of cumulative pulses, when the signal photons are less than 0.1 per pulse, the range accuracy of 4.1 cm and 5.3 cm are obtained under the background noise of 7.6 MHz and 5.1 MHz, respectively. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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11 pages, 3559 KiB

Open AccessCommunication

The Acceleration Phenomenon of Shock Wave Induced by Nanosecond Laser Irradiating Silicon Assisted by Millisecond Laser

by Jingyi Li, Wei Zhang, Ye Li and Guangyong Jin

Photonics 2023, 10(3), 260; https://doi.org/10.3390/photonics10030260 - 28 Feb 2023

Cited by 1 | Viewed by 1984

Abstract

The propagating evolution of shock waves induced by a nanosecond pulse laser (ns laser) irradiating silicon assisted by a millisecond pulse laser (ms laser) is investigated experimentally. A numerical model of 2D axisymmetric two-phase flow is established to obtain the spatial distribution of [...] Read more.

The propagating evolution of shock waves induced by a nanosecond pulse laser (ns laser) irradiating silicon assisted by a millisecond pulse laser (ms laser) is investigated experimentally. A numerical model of 2D axisymmetric two-phase flow is established to obtain the spatial distribution of shock wave velocity. Two types of shock wave acceleration phenomenon are found. The mechanism of the shock wave acceleration phenomenon is discussed. The experimental and numerical results show that the initial stage of ms laser-induced plasma can provide the initial ions to increase probability of collision ionization between free electrons and vapor atoms. The velocity of the ns laser-induced shock wave is accelerated. Furthermore, the ms laser-induced plasma as the propagation medium can also accelerate the ns laser-induced shock wave. The shock wave acceleration methods obtained in this paper can promote the development of laser propulsion technology. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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9 pages, 3038 KiB

Open AccessCommunication

Simulation Study of Phase-Driven Multichannel Nano-Optical Conveyor Belt Using Rectangular Gratings

by Chunyan Bai, Xiangcai Ma, Qian Cao, Saima Kanwal and Peizhen Qiu

Photonics 2023, 10(2), 201; https://doi.org/10.3390/photonics10020201 - 13 Feb 2023

Viewed by 1613

Abstract

A nano-optical conveyor belt is a unique type of near-field optical tweezer, capable not only of capturing nanoparticles, but also transporting them. In this study, we propose a multichannel nano-optical conveyer, based on a simple rectangular distributed grating array. The design was optimized [...] Read more.

A nano-optical conveyor belt is a unique type of near-field optical tweezer, capable not only of capturing nanoparticles, but also transporting them. In this study, we propose a multichannel nano-optical conveyer, based on a simple rectangular distributed grating array. The design was optimized by varying the number of slits in the gratings, and particle transport was achieved by adjusting the phase difference of the excitation beams. Simulation and calculation results indicate that multiple optical traps and parallel transport channels can be generated by exciting the gratings with four incident beams. The optical force and trapping potential were used to confirm that 20 nm metallic nanoparticles can be stably attracted to the traps and dynamically transported along channels by adjusting the phase of the excitation beams. Compared to existing nano-photon conveyors, this design boasts a straightforward structure and exceptional performance, offering a promising new approach to particle manipulation. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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10 pages, 2259 KiB

Open AccessCommunication

Quasi-Guided Modes Supported by a Composite Grating Structure with Alternating Element Widths

by Min Sun and Zhanghua Han

Photonics 2023, 10(2), 110; https://doi.org/10.3390/photonics10020110 - 20 Jan 2023

Viewed by 2033

Abstract

The efficiency of many optical processes is significantly dependent on the magnitude of the electric field. In this context, many artificially made resonating structures have been investigated to enhance light–matter interactions and facilitate the creation of practical applications. While metal–based terahertz metamaterials have [...] Read more.

The efficiency of many optical processes is significantly dependent on the magnitude of the electric field. In this context, many artificially made resonating structures have been investigated to enhance light–matter interactions and facilitate the creation of practical applications. While metal–based terahertz metamaterials have been extensively investigated for this purpose, their performances are mainly limited by the poor confinement of terahertz waves on metal surfaces, exhibiting low resonance quality factors. In this work, we propose and investigate a simple yet novel scheme of enhancing wave–matter interactions in the terahertz region by exploiting the phenomenon of quasi–guided modes. The quasi-guided modes with ultra–high quality factors and huge local field enhancement can be achieved by manipulating the guided modes supported by a slab waveguide. The guided modes with the dispersion lines below the light line have infinite Q factors and can not be accessed from external space. By using a new type of composite grating composed of two ridge grating arrays with alternating ridge widths, the grating period is doubled, leading to a folding of the first Brillouin Zone and the flipping of the dispersion lines to be above the light line. Then, the guided modes will be transitioned into new quasi–guided modes with the possibility of free–space excitation while the Q factors are determined by the level of period–doubling perturbation. The presented results of realizing quasi–guided modes can be extended to other structures, providing a novel means of manipulating light–matter interactions. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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14 pages, 7264 KiB

Open AccessArticle

Influence of Exposure Parameters on Nanoliquid-Assisted Glass Drilling Process Using CO₂ Laser

by Mohaimen Najah Mahdi, Ahmed Issa, Hala Salman Hasan, Ahmed R. Al-Hamaoy and Muammel M. Hanon

Photonics 2023, 10(1), 89; https://doi.org/10.3390/photonics10010089 - 13 Jan 2023

Viewed by 1798

Abstract

Liquid-assisted laser processing (LALP) is implemented using a 10.6 μm continuous-wave (CW) CO₂ laser to drill holes in 1.1 mm thick soda-lime glass substrates fully immersed in a nanoliquid bath. The nanoliquid bath consisted of de-ionized water and carbon nano-particles (CNPs) of [...] Read more.

Liquid-assisted laser processing (LALP) is implemented using a 10.6 μm continuous-wave (CW) CO₂ laser to drill holes in 1.1 mm thick soda-lime glass substrates fully immersed in a nanoliquid bath. The nanoliquid bath consisted of de-ionized water and carbon nano-particles (CNPs) of different wt.%. The study focuses on the influence of exposure time (T_E, [s]), laser beam power (P, [W]) and number of pulses (N_P) on resulting geometrical features, namely, crack length (CL, [mm]), inlet diameter (D_INLET, [mm]) and exit diameter (D_EXIT, [mm]). The processed samples were characterized using an optical microscope. Findings show that LALP with investigated ranges of control parameters T_E (0.5–1.5 s), P (20–40 W) and N_P (1–6 pulses) led to successful production of drilled holes having CL range (0.141 to 0.428 mm), D_INLET range (0.406 to 1.452 mm) and D_EXIT range (0.247 to 1.039 mm). It was concluded that increasing T_E alone leads to increasing CL, D_INLET and D_EXIT, while keeping a good balance among the control parameters, especially T_E and N_P, will result in reduced CL values. Moreover, process statistical models were developed using statistical analysis of variance (ANOVA). These models can be used to further understand and control the process within the investigated ranges of control and response parameters. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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7 pages, 1587 KiB

Open AccessCommunication

1.55 μm Narrow-Linewidth Pulsed Laser Based on MgO:PPLN

by Yaling Yang, Guorui Lv, Lei Guo, Haiping Xu, Hui Kong, Jiaqi Wen, Jintian Bian, Qing Ye, Kejian Yang and Jingliang He

Photonics 2023, 10(1), 77; https://doi.org/10.3390/photonics10010077 - 9 Jan 2023

Cited by 1 | Viewed by 2071

Abstract

A high-power narrow-linewidth 1.55 μm pulsed laser, based on MgO:PPLN OPO, has been achieved using a F–P etalon. The pump source is a 1064 nm acousto-optical (AO) Q-switched Nd:YAG laser with a repetition rate of 10 kHz. Under the maximum pump power of [...] Read more.

A high-power narrow-linewidth 1.55 μm pulsed laser, based on MgO:PPLN OPO, has been achieved using a F–P etalon. The pump source is a 1064 nm acousto-optical (AO) Q-switched Nd:YAG laser with a repetition rate of 10 kHz. Under the maximum pump power of 18 W, the signal output power of 2.57 W is demonstrated at 1551.1 nm with a linewidth of 0.07 nm, corresponding to a slope efficiency of 16.1%. Different from traditional inversion lasers, the narrow-linewidth wavelength tunability of approximately 1.55 μm can be realized by changing the temperature. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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8 pages, 4052 KiB

Open AccessArticle

Efficient Third-Harmonic Generation by Inhomogeneous Quasi-Phase-Matching in Quadratic Crystals

by Obid I. Sabirov, Gaetano Assanto and Usman K. Sapaev

Photonics 2023, 10(1), 76; https://doi.org/10.3390/photonics10010076 - 9 Jan 2023

Cited by 3 | Viewed by 1584

Abstract

We investigate the generation of optical third-harmonic frequency in quadratic crystals with a nonlinear domain lattice optimized with the aid of a random number generator. In the developed Monte Carlo algorithm and numerical experiments, we consider domain thicknesses to be taking either the [...] Read more.

We investigate the generation of optical third-harmonic frequency in quadratic crystals with a nonlinear domain lattice optimized with the aid of a random number generator. In the developed Monte Carlo algorithm and numerical experiments, we consider domain thicknesses to be taking either the values d₁ or d₂, with d₁ and d₂ being the coherence lengths for the cascaded parametric interactions

2 ω = ω + ω

and

3 ω = 2 ω + ω

, respectively. We focus on the cases with single segments formed by equal and/or different domains, showing that frequency tripling can be achieved with high conversion efficiency from an arbitrary input wavelength. The presented approach allows one to accurately determine the optimized random alternation of domain thicknesses d₁ and d₂ along the propagation length. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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16 pages, 771 KiB

Open AccessArticle

Critical Laser Intensity of Phase-Matched High-Order Harmonic Generation in Noble Gases

by Björn Minneker, Robert Klas, Jan Rothhardt and Stephan Fritzsche

Photonics 2023, 10(1), 24; https://doi.org/10.3390/photonics10010024 - 26 Dec 2022

Cited by 1 | Viewed by 2038

Abstract

The efficient generation of high-order harmonic radiation has been a challenging task since the early days of strong-field physics. An essential requirement to achieve efficient high-order harmonic generation inside a gas medium is the phase matching of the high-order harmonic radiation and the [...] Read more.

The efficient generation of high-order harmonic radiation has been a challenging task since the early days of strong-field physics. An essential requirement to achieve efficient high-order harmonic generation inside a gas medium is the phase matching of the high-order harmonic radiation and the incident laser pulse. The dominant contribution to the wave–vector mismatch

Δ k

is associated with the ionization probability of the medium. In this work, we derive two analytical formulas to calculate the critical intensity of a general linearly polarized laser pulse that obey the phase-matching condition

Δ k = 0

. The analytic formulas are valid in the tunneling regime (ADK model) and the regime of the tunnel and multi-photon ionization (PPT model), respectively. We compare our results to numerical computations and discuss the scaling of the critical intensity depending on the pulse duration and the wavelength of a realistic incident laser pulse. The analytical approach demonstrated in this work is highly accurate and can compete with the existing numerical computational methods by an error of less than 1% and a decrease in the computation time of approximately 4 to 6 orders of magnitude. This enables complex theoretical studies of the efficiency scaling in HHG or to consider the effects of ground state depletion efficiently. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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15 pages, 3059 KiB

Open AccessArticle

Effect of Lidar Receiver Field of View on UAV Detection

by Zijian Chen, Yu Miao, Dan Tang, Hao Yang and Wenwu Pan

Photonics 2022, 9(12), 972; https://doi.org/10.3390/photonics9120972 - 11 Dec 2022

Cited by 1 | Viewed by 2274

Abstract

Researchers have shown that single-photon light detection and ranging (lidar) is highly sensitive and has a high temporal resolution. Due to the excellent beam directivity of lidar, most applications focus on ranging and imaging. Here, we present a lidar detection system for night [...] Read more.

Researchers have shown that single-photon light detection and ranging (lidar) is highly sensitive and has a high temporal resolution. Due to the excellent beam directivity of lidar, most applications focus on ranging and imaging. Here, we present a lidar detection system for night environments. Different from MEMS, we choose a large divergence rather than scanning to detect unmanned aerial vehicles (UAVs). Collection and detection are achieved through the use of high-efficiency optical devices. With time-correlated single photon counting (TCSPC), we performed subsequent drone search work at centimeter resolution. We believe that we have developed a new technique for detecting UAVs. We show how the field of view influences the detection process. For some key areas of air defense, it is extremely necessary to find UAVs quickly and in a timely manner. In short, the results represent an important step toward practical, low-power drone detection using lidar. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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13 pages, 2612 KiB

Open AccessArticle

Laser Driven Electron Acceleration from Near-Critical Density Targets towards the Generation of High Energy γ-Photons

by Iuliana-Mariana Vladisavlevici, Daniel Vizman and Emmanuel d’Humières

Photonics 2022, 9(12), 953; https://doi.org/10.3390/photonics9120953 - 9 Dec 2022

Cited by 3 | Viewed by 2021

Abstract

In this paper, we investigate the production of high energy gamma photons at the interaction between an ultra-high intensity laser pulse with an energetic electron beam and with a near-critical density plasma for the laser intensity varying between

10^{19}

–

10^{23}

[...] Read more.

In this paper, we investigate the production of high energy gamma photons at the interaction between an ultra-high intensity laser pulse with an energetic electron beam and with a near-critical density plasma for the laser intensity varying between

10^{19}

–

10^{23}

W/cm

^{2}

. In the case of the interaction with an electron beam, and for the highest laser intensities considered, the electrons lose almost all their energy to emit gamma photons. In the interaction with a near-critical density plasma, the electrons are first accelerated by the laser pulse up to GeV energies and further emit high energy radiation. A maximum laser-to-photons conversion coefficient of

30 %

is obtained. These results can be used for the preparation of experiments at the Apollon and ELI laser facilities for the investigation of the emission of high energy

γ

-photons and to study the electron-positron pair creation in the laboratory. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 2956 KiB

Open AccessArticle

Photonic Integrated Circuit for Optical Phase Control of 1 × 4 Terahertz Phased Arrays

by Peng Lu, Thomas Haddad, Jonas Tebart, Chris Roeloffzen and Andreas Stöhr

Photonics 2022, 9(12), 902; https://doi.org/10.3390/photonics9120902 - 25 Nov 2022

Cited by 9 | Viewed by 3633

Abstract

In this manuscript, we report on a 1 × 4 optical beam forming network (OBFN) chip using optical phase shifters (OPSs) based on thermo-optically controlled optical ring resonators (ORRs) for 1D beam steering at 0.3 THz. The 1 × 4 OBFN chip consists [...] Read more.

In this manuscript, we report on a 1 × 4 optical beam forming network (OBFN) chip using optical phase shifters (OPSs) based on thermo-optically controlled optical ring resonators (ORRs) for 1D beam steering at 0.3 THz. The 1 × 4 OBFN chip consists of four OPSs and is fabricated using TriPleX technology. Each of the four OPSs is realized by two cascaded identical ORRs, to reach a phase shift of 2π. To allow transfer of the optical phase shift to the THz domain by optical heterodyning in high-frequency 1.55 µm modified uni-travelling carrier photodiodes, the ORRs are designed such that one carrier of the optical heterodyne signal is at the ORR’s resonance frequency, whereas the second optical heterodyne signal is at its off-resonance. By adjusting the resonance frequencies of the two ORRs in each OPS synchronously, a relative phase variation between two optical heterodyne carriers of up to 2π with a tuning efficiency of 0.058 W/π, is experimentally demonstrated. Due to the dispersive power transmission loss of the ORRs, phase tuning leads to a power variation of the optical heterodyne-generated signals up to 3.8 dB, which is experimentally characterized at 0.295 THz. It is shown numerically that this power variation only has a minor impact on the steering performance of a 1 × 4 phased array. The determined beam direction deviation and maximum absolute radiation power change are smaller than 1° and 2 dB, respectively. By sweeping the phase difference between two adjacent THz antennas in the 1 × 4 phased array, from −120° to 120°, a beam steering range of ~62° is demonstrated numerically at 0.295 THz. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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11 pages, 444 KiB

Open AccessArticle

Collisions of Electrons with Alkali, Alkaline and Complex Atoms Relevant to Solar and Stellar Atmospheres

by Moncef Derouich, Saleh Qutub, Fainana Mustajab and Badruddin Zaheer Ahmad

Universe 2022, 8(12), 613; https://doi.org/10.3390/universe8120613 - 23 Nov 2022

Viewed by 1427

Abstract

In solar and stellar atmospheres, atomic excitation by impact with electrons plays an important role in the formation of spectral lines. We make use of available experimental and theoretical cross-sections to calculate the excitation rates in s–p transitions of alkali and [...] Read more.

In solar and stellar atmospheres, atomic excitation by impact with electrons plays an important role in the formation of spectral lines. We make use of available experimental and theoretical cross-sections to calculate the excitation rates in s–p transitions of alkali and alkaline atoms through collisions with electrons. Then, we infer a general formula for calculating the excitation rates by using genetic programming numerical methods. We propose an extension of our approach to deduce collisional excitation rates for complex atoms and atoms with hyperfine structure. Furthermore, the developed method is also applied to determine collisional polarization transfer rates. Our results are not specific to a given atom and can be applied to any s–p atomic transition. The accuracy of our results is discussed. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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10 pages, 4376 KiB

Open AccessArticle

Decoherence of Higher Order Orbital Angular Momentum Entangled State in Non-Kolmogorov Turbulence

by Xiang Yan, Pengfei Zhang, Boying Wu and Jinghui Zhang

Photonics 2022, 9(11), 808; https://doi.org/10.3390/photonics9110808 - 27 Oct 2022

Viewed by 1315

Abstract

The decay of OAM entanglement in non-Kolmogorov turbulence has been numerically evaluated. In this work, we explore the evolution of OAM entanglement with higher-order OAM mode in the weak scintillation regime. In particular, the results of the numerical evaluation show that the OAM [...] Read more.

The decay of OAM entanglement in non-Kolmogorov turbulence has been numerically evaluated. In this work, we explore the evolution of OAM entanglement with higher-order OAM mode in the weak scintillation regime. In particular, the results of the numerical evaluation show that the OAM entanglement state with higher value of the azimuthal mode and larger radial quantum number survives over a longer distance. Meanwhile, the beam parameters and turbulence parameters usually have significant influences on OAM entanglement. In addition, it is demonstrated that the effect of turbulence on the OAM entanglement is the most serious when the generalized exponent is around 3.07. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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14 pages, 2574 KiB

Open AccessArticle

Thermodynamic Functions of a Metal Exposed to High Energy Densities in Compressed and Expanded States

by Nikolay B. Volkov and Alexander I. Lipchak

Condens. Matter 2022, 7(4), 61; https://doi.org/10.3390/condmat7040061 - 27 Oct 2022

Cited by 2 | Viewed by 1861

Abstract

The development of a wide-range phenomenological model of metal with a small number of adjustable parameters for studying the behavior of metals in expanded and compressed states under the exposition of high energy density fluxes is the objective of the paper present. Both [...] Read more.

The development of a wide-range phenomenological model of metal with a small number of adjustable parameters for studying the behavior of metals in expanded and compressed states under the exposition of high energy density fluxes is the objective of the paper present. Both the reference data, methods of the quantum-statistical model of the atom, the density functional theory, and the requirement to the expanded and compressed states description of metal should be consistent on their boundary were used in the model. The expressions for thermodynamic functions and the critical parameters of expanded iron were obtained within the framework of the soft sphere model. The Grüneisen parameters calculated for the expanded and compressed states of the metal appear to be in good agreement with each other was shown. A calculation technique of the ion component average charge of the metal in expanded and compressed states is proposed. The experimentally defined volume range of V/V₀ = 3–4 in which the character of iron conductivity changes from metallic to non-metallic includes the obtained in frameworks of our approach value of the critical volume: V/V₀ = 3.802 was established. The behavior of the average charge of the ion component is discussed. The contribution of the thermal electrons to the thermodynamic functions is evaluated. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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9 pages, 3900 KiB

Open AccessArticle

Dual-Wavelength Continuous-Wave and Passively Q-Switched Alexandrite Laser at 736.7 nm and 752.8 nm

by Hongyi Lin, Shangfeng Bao, Xiao Liu, Shuo Song, Zhiwei Wen and Dong Sun

Photonics 2022, 9(10), 769; https://doi.org/10.3390/photonics9100769 - 14 Oct 2022

Cited by 2 | Viewed by 1889

Abstract

A dual-wavelength continuous-wave (CW) and passively Q-switched alexandrite laser based on a MoS₂ saturable absorber (SA) operating at 736.7 nm and 752.8 nm with a simple and compact 18 mm plano–plano resonator is reported. In the CW mode, the output power is [...] Read more.

A dual-wavelength continuous-wave (CW) and passively Q-switched alexandrite laser based on a MoS₂ saturable absorber (SA) operating at 736.7 nm and 752.8 nm with a simple and compact 18 mm plano–plano resonator is reported. In the CW mode, the output power is 1014 mW at the linear-polarized pump power of 5.44 W, with a slope efficiency of 28.7%. In the pulsed operation, the narrowest pulse width and the maximal peak power are 154 ns and 10.6 W, respectively. This laser can be used to generate 8.71 THz-wave light based on a suitable nonlinear optical crystal. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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8 pages, 2418 KiB

Open AccessCommunication

Tunable High-Q Factor Substrate for Selectively Enhanced Raman Scattering

by Zhengqing Qi, Jinhuan Li, Peng Chen, Lingling Zhang and Ke Ji

Photonics 2022, 9(10), 755; https://doi.org/10.3390/photonics9100755 - 11 Oct 2022

Cited by 2 | Viewed by 1486

Abstract

Most Surface-enhanced Raman scattering (SERS) substrates enhance all the Raman signals in a relative broad spectral range. The substrates enhance both the interested and background signals together. To improve the identification of target molecules from numerous background ones, substrates with multi high-quality (Q) [...] Read more.

Most Surface-enhanced Raman scattering (SERS) substrates enhance all the Raman signals in a relative broad spectral range. The substrates enhance both the interested and background signals together. To improve the identification of target molecules from numerous background ones, substrates with multi high-quality (Q) factor resonance wavelengths can be designed to achieve the selective enhancement of specific Raman transitions. When the resonance frequencies are modulated to match the excitation and Raman scattering frequencies, the detection of the target molecule can be more effective. In this paper, we design a tunable high-Q SERS substrate with periodic silver bowtie nanoholes on silica spacer and silver film. The substrate possessed three high-Q and high electric field resonance modes, which resulted from the interaction of the localized surface plasmon resonance (LSPR) of the bowtie nanoholes, the surface plasmon polariton (SPP) of the period bowtie nanoholes and the Fabry–Perot (FP) resonance between the bowtie and silver film bottom. The interaction between these resonance modes resulted in not only a higher quality (Q) factor, but also a higher electric field, which can be employed to realize a potential substrate in high-sensitivity and selective-detection fields. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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9 pages, 4053 KiB

Open AccessCommunication

Optical-Frequency-Comb Generation Based on Single-Tone Modulation and Four-Wave Mixing Effect in One Single Semiconductor Optical Amplifier

by Zeyu Tan and Lirong Huang

Photonics 2022, 9(10), 746; https://doi.org/10.3390/photonics9100746 - 9 Oct 2022

Viewed by 2030

Abstract

We propose a novel optical-frequency-comb (OFC) generation scheme based on single-tone modulation and the four-wave mixing (FWM) effect in one single semiconductor optical amplifier (SOA) modulated by a radio frequency (RF) current. A comprehensive broad-band dynamic model, which considers single-tone modulation and the [...] Read more.

We propose a novel optical-frequency-comb (OFC) generation scheme based on single-tone modulation and the four-wave mixing (FWM) effect in one single semiconductor optical amplifier (SOA) modulated by a radio frequency (RF) current. A comprehensive broad-band dynamic model, which considers single-tone modulation and the FWM effect, is presented. The simulated results show that, although only one single continuous-wave light is input into the SOA, an OFC with a large number of frequency components can be achieved as a result of single-tone modulation and the FWM effect in the SOA. The number of comb lines and the spectral bandwidth of the OFC increase by raising the amplitude of the RF modulation current. Increasing the input light power can increase the average optical power of the OFC. The frequency interval is tunable within a certain range by tuning the frequency of the RF modulation current injected into the SOA. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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15 pages, 2308 KiB

Open AccessArticle

Programmable Parallel Optical Logic Gates on a Multimode Waveguide Engine

by Tao Chen, Zhangqi Dang, Zhenming Ding and Ziyang Zhang

Photonics 2022, 9(10), 736; https://doi.org/10.3390/photonics9100736 - 8 Oct 2022

Cited by 4 | Viewed by 2212

Abstract

Optical logic gates have been proposed and demonstrated on a function programmable waveguide engine constructed using buried silicon nitride waveguides in polymer and a set of thermal electrodes. The device can perform logic AND or OR operations for the input signals A and [...] Read more.

Optical logic gates have been proposed and demonstrated on a function programmable waveguide engine constructed using buried silicon nitride waveguides in polymer and a set of thermal electrodes. The device can perform logic AND or OR operations for the input signals A and B, each containing two bits of information, in parallel. The input signals, in the form of binary current values in the electronic domain, are applied to a subset of thermal electrodes, while the computed logic states are converted to optical intensity variations at the single-mode waveguide outputs. The rest of the electrodes work as weights to define the device function, either AND or OR, by adjusting the light interference in the multimode waveguide through thermo-optic effect. Simulations were first performed to reveal the nonlinear response of the received light intensity with respect to the applied current, thus allowing complex and effective manipulation of the light field on the waveguide engine. After chip fabrication and system integration, 65,536 experiments were performed automatically. The data are fed into a sorting program to find the valid settings that satisfy the respective truth table out of the 283,852,800 possible input/weight/output combinations. Four cases of operations for the AND and OR gates are presented in the end, with different bar and contrast values. This simple, low-cost yet powerful engine may be further developed for applications in on-chip photonic computing and signal switching. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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10 pages, 2916 KiB

Open AccessCommunication

Theoretical and Experimental Investigations of Tunable Microwave Signal Generation Based on a 1-GHz All-Polarization-Maintaining Mode-Locked Fiber Laser

by Denghui Song, Ke Yin, Sirui Kong, Xiya Chen and Zhongjie Xu

Photonics 2022, 9(10), 717; https://doi.org/10.3390/photonics9100717 - 1 Oct 2022

Cited by 1 | Viewed by 1559

Abstract

Photonics-based microwave generation brings the advantages of photonic oscillators, such as high stability, wide bandwidth, and low loss, to the microwave domain. In this paper, the generation of tunable microwave signals was investigated both theoretically and experimentally based on an all-polarization-maintaining 1-GHz mode-locked [...] Read more.

Photonics-based microwave generation brings the advantages of photonic oscillators, such as high stability, wide bandwidth, and low loss, to the microwave domain. In this paper, the generation of tunable microwave signals was investigated both theoretically and experimentally based on an all-polarization-maintaining 1-GHz mode-locked fiber laser. Based on beating between two highly chirped optical pulse trains with a relative time delay at the photodetector, tunable microwave signals could be obtained. The numerical simulations show that 40 GHz or higher microwave signals could be obtained by tuning the time delay and dispersion. To experimentally validate the theoretical model, the generation of tunable microwave signals from 2–4 GHz was demonstrated. Due to the utilization of polarization-maintaining devices, the optical output has a high degree of linear polarization of more than 99%, which verifies the enhanced system stability. These demonstrations are imperative for solidifying the advancements of recent years and could promote the utilization of photonics-based microwave generation in microwave photonics. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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14 pages, 2630 KiB

Open AccessArticle

Goos–Hänchen Lateral Displacements and Angular Deviations: When These Optical Effects Offset Each Other

by Stefano De Leo, Luca Maggio and Moreno d’Ambrosio

Photonics 2022, 9(9), 643; https://doi.org/10.3390/photonics9090643 - 7 Sep 2022

Cited by 3 | Viewed by 1787

Abstract

For optical beams transmitted by a right-angle prism, the Goos–Hänchen shift can never be seen as a pure effect. Indeed, the lateral displacement, caused by the total internal reflection, will always be accompanied by angular deviations generated by the transmission through the incoming [...] Read more.

For optical beams transmitted by a right-angle prism, the Goos–Hänchen shift can never be seen as a pure effect. Indeed, the lateral displacement, caused by the total internal reflection, will always be accompanied by angular deviations generated by the transmission through the incoming and outgoing interfaces. This combined effect can be analyzed by using the Taylor expansion of the Fresnel coefficients. The analytic expression found for the transmitted beam allows us to determine the beam parameters, the incidence angles, and the axial distance for which lateral displacements are compensated by angular deviations. Proposals to optimize experimental implementations are also briefly discussed. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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15 pages, 7339 KiB

Open AccessEditor’s ChoiceArticle

A Plasma-Based Decontamination Process Reveals Potential for an in-Process Surface-Sanitation Method

by Thomas Weihe, Uta Schnabel, Mathias Andrasch, Jörg Stachowiak, Frank Tübbecke and Jörg Ehlbeck

Plasma 2022, 5(3), 351-365; https://doi.org/10.3390/plasma5030027 - 6 Sep 2022

Cited by 4 | Viewed by 1878

Abstract

Methods, which use an indirect plasma treatment for the inactivation of microorganisms in foods, claim a vastly growing field of research. This paper presents a method that uses plasma-processed air (PPA) as a sanitizer. In addition to a sanitation concept for the decontamination [...] Read more.

Methods, which use an indirect plasma treatment for the inactivation of microorganisms in foods, claim a vastly growing field of research. This paper presents a method that uses plasma-processed air (PPA) as a sanitizer. In addition to a sanitation concept for the decontamination of produce in the value chain, the presented method offers a possible application as an “in-process” surface sanitation. PPA provides antimicrobial-potent species, which are predominantly reactive nitrogen species (RNS); this has an outstanding groove penetration property. In an experimental approach, surfaces, made from materials, which are frequently used for the construction of food-processing plants, were inoculated with different microorganisms. Listeria monocytogenes (ATCC 15313), Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 10538), Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 43971), and Salmonella enterica subsp. enterica serovar Enteritidis (ATCC 13076) are all microorganisms that frequently appear in foods and possess the risk for cross-contamination from the plant to the produce or vice versa. The contaminated samples were treated for various treatment times (1–5 min) with PPA of different antimicrobial potencies. Subsequently, the microbial load on the specimens was determined and compared with the load of untreated samples. As a result, reduction factors (RF) up to several log₁₀-steps were obtained. Although surface and the bacterial strain showed an influence on the RF, the major influence was seen by a prolongation of the treatment time and an increase in the potency of the PPA. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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16 pages, 10613 KiB

Open AccessArticle

Polarization-Insensitive Graphene Modulator Based on Hybrid Plasmonic Waveguide

by Songyue Liu, Manzhuo Wang, Tingyu Liu, Yan Xu, Jianbo Yue, Yunji Yi, Xiaoqiang Sun and Daming Zhang

Photonics 2022, 9(9), 609; https://doi.org/10.3390/photonics9090609 - 28 Aug 2022

Cited by 8 | Viewed by 1942

Abstract

A polarization-insensitive graphene-assisted electro-optic modulator is proposed. The orthogonal T-shaped metal slot hybrid plasmonic waveguide allows the polarization-independent propagation of transverse electric field mode and complex mode. By the introduction of dual-layer graphene on the ridge waveguide, the polarization-insensitive modulation depths of the [...] Read more.

A polarization-insensitive graphene-assisted electro-optic modulator is proposed. The orthogonal T-shaped metal slot hybrid plasmonic waveguide allows the polarization-independent propagation of transverse electric field mode and complex mode. By the introduction of dual-layer graphene on the ridge waveguide, the polarization-insensitive modulation depths of the TE mode and complex mode are 0.511 dB/µm and 0.502 dB/µm, respectively. The 3 dB bandwidth of the modulator we have proposed is about 127 GHz at the waveguide length of 20 μm. The power consumption of 72 fJ/bit promised potential graphene electro-optic modulator applications for on-chip interconnected information transfer and processing. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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11 pages, 7175 KiB

Open AccessCommunication

Holographic Encryption Applications Using Composite Orbital Angular Momentum Beams

by Nian Zhang, Baoxing Xiong, Xiang Zhang and Xiao Yuan

Photonics 2022, 9(9), 605; https://doi.org/10.3390/photonics9090605 - 26 Aug 2022

Cited by 5 | Viewed by 2312

Abstract

Optical orbital angular momentum (OAM) holography has been developed and implemented as a vital method for optical encryption. However, OAM holography can only be encoded and decoded with an OAM beam, which limits the level of optical encryption. Here, composite OAM beams are [...] Read more.

Optical orbital angular momentum (OAM) holography has been developed and implemented as a vital method for optical encryption. However, OAM holography can only be encoded and decoded with an OAM beam, which limits the level of optical encryption. Here, composite OAM beams are introduced using a computer-generated hologram (CGH) for holographic encryption. The target image is encoded with composite helical mode indices, and the OAM holographic image can only be reconstructed under a specific illuminating composite OAM beam. The experimental results are consistent with the theoretical design and numerical simulations, verifying that composite OAM beams can provide a higher security level for optical holographic encryption. The proposed method can be used to enhance anti-counterfeiting applications, secure communication systems, and imaging systems. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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9 pages, 1756 KiB

Open AccessArticle

High-Power, Narrow-Linewidth Distributed-Feedback Quantum-Cascade Laser for Molecular Spectroscopy

by Mathieu Bertrand, Aleksandr Shlykov, Mehran Shahmohamadi, Mattias Beck, Stefan Willitsch and Jérôme Faist

Photonics 2022, 9(8), 589; https://doi.org/10.3390/photonics9080589 - 19 Aug 2022

Cited by 3 | Viewed by 2577

Abstract

Quantum cascade lasers are versatile light sources in the mid-infrared range for molecular spectroscopy which find a wide range of applications from high-resolution studies to sensing. While devices with either high power or narrow spectral linewidth have previously been reported, there is still [...] Read more.

Quantum cascade lasers are versatile light sources in the mid-infrared range for molecular spectroscopy which find a wide range of applications from high-resolution studies to sensing. While devices with either high power or narrow spectral linewidth have previously been reported, there is still a lack of sources combining both of these characteristics which are particularly important for precision measurements of weak spectroscopic transitions. In this article, we describe and characterize a novel master-oscillator power-amplifier distributed-feedback quantum cascade laser designed to fill this gap. At an output power of 300 mW, the device features a free-running linewidth of 1.3 MHz, measured with a frequency discriminator technique, at an emission wavenumber of 2185 cm

^{- 1}

. This linewidth is sufficiently narrow to enable a further reduction by a tight lock to a high-Q oscillator. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 2667 KiB

Open AccessArticle

Design of a Broadband Perfect Solar Absorber Based on a Four-Layer Structure with a Cross-Shaped Resonator and Triangular Array

by Yushan Chen, Kewei You, Jianze Lin, Junwei Zhao, Wenzhuang Ma, Dan Meng, Yuyao Cheng and Jing Liu

Photonics 2022, 9(8), 565; https://doi.org/10.3390/photonics9080565 - 11 Aug 2022

Cited by 6 | Viewed by 2052

Abstract

As solar energy is a low-cost and clean energy source, there has been a great deal of interest in how to harvest it. To absorb solar energy efficiently, we designed a broadband metamaterial absorber based on the principle of Fabry–Pérot (FP) cavities and [...] Read more.

As solar energy is a low-cost and clean energy source, there has been a great deal of interest in how to harvest it. To absorb solar energy efficiently, we designed a broadband metamaterial absorber based on the principle of Fabry–Pérot (FP) cavities and surface plasmon resonance (SPR). We propose a broadband perfect absorber consisting of a four-layer structure of silica–tungsten–silica–titanium (SiO₂–W–SiO₂–Ti) for the incident light wavelength range of 300–2500 nm. The structure achieves perfect absorption of incident light in the wavelength range of 351.8–2465.0 nm (absorption > 90%), with an average absorption of 96.3%. The advantage of our proposed structure is that it combines the characteristics of both high and broadband absorption, and has high overall absorption efficiency for solar radiation. It is also independent of polarization and insensitive to incident angle. We investigated how absorption was affected by different structures, materials, geometric parameters, and refractive indices for different dielectric materials, and we explored the reasons for high absorption. This structure is refractory and ultrathin, and it offers a good tradeoff between bandwidth and absorption. It therefore has premium application prospects and value. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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17 pages, 8631 KiB

Open AccessArticle

Planar Waveguide-Based Fiber Spectrum Analyzer Mountable to Commercial Camera

by Xinhong Jiang and Ziyang Zhang

Photonics 2022, 9(7), 456; https://doi.org/10.3390/photonics9070456 - 28 Jun 2022

Cited by 4 | Viewed by 2055

Abstract

We present the design of a planar spectrometer that separates the wavelength channels from an input fiber and focuses the spectral lines onto a camera without any free-space optical elements. The geometric arrangements of the waveguides to achieve different spectroscopic parameters are explained [...] Read more.

We present the design of a planar spectrometer that separates the wavelength channels from an input fiber and focuses the spectral lines onto a camera without any free-space optical elements. The geometric arrangements of the waveguides to achieve different spectroscopic parameters are explained in detail, allowing adjustable focal lengths, high spectral resolution, and broad free spectral range. The optical chip is fabricated on a low-cost polymer platform as proof of concept. The optical spectrum of a multiwavelength laser is measured by the proposed device, and the result is in good agreement with a commercial optical spectrum analyzer. The large focal depth of the chip allows an optical assembly of much relaxed alignment accuracy. We demonstrate a tube design to encapsulate the chip fixed with the input fiber. The assembly is then mounted to a commercial camera with standard C-mount threading as a convenient fiber spectrum analyzer without customized detectors and circuits. Our design may provide a low-cost and versatile solution for the development of compact spectroscopic equipment. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 10921 KiB

Open AccessArticle

Beam Smoothing Based on Prism Pair for Multistep Pulse Compressor in PW Lasers

by Shuman Du, Xiong Shen, Wenhai Liang, Peng Wang and Jun Liu

Photonics 2022, 9(7), 445; https://doi.org/10.3390/photonics9070445 - 23 Jun 2022

Cited by 4 | Viewed by 2267

Abstract

Ultra-short, ultra-intense lasers provide unprecedented experimental tools and extreme physical conditions, enabling the exploration of the frontiers of basic physics. Recently, a multistep pulse compressor (MPC) method was proposed to overcome the limitations of the size and the damage threshold of gratings in [...] Read more.

Ultra-short, ultra-intense lasers provide unprecedented experimental tools and extreme physical conditions, enabling the exploration of the frontiers of basic physics. Recently, a multistep pulse compressor (MPC) method was proposed to overcome the limitations of the size and the damage threshold of gratings in the compressor for the realization of a higher-peak-power laser. In the MPC method, beam smoothing is an important process in the pre-compressor. In this study, beam smoothing based on prism pairs is investigated, and the spatial profiles, as well as spectral dispersion properties, are analyzed. The simulation results demonstrate that the prism pair can effectively smooth the laser beam. Furthermore, beam smoothing is found to be more efficient with a shorter separation distance if two prism pairs are arranged to induce spatial dispersion in one or two directions. The beam smoothing results obtained in this study will help optimize optical designs in petawatt (PW) laser systems, thereby improving their output and operational safety. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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9 pages, 1986 KiB

Open AccessArticle

All-Dielectric Structural Colors with Lithium Niobate Nanodisk Metasurface Resonators

by Yuting Zhou, Qingyu Wang, Zhiqiang Ji and Pei Zeng

Photonics 2022, 9(6), 402; https://doi.org/10.3390/photonics9060402 - 8 Jun 2022

Cited by 6 | Viewed by 2762

Abstract

Lithium niobate (LN) is a promising optical material, its micro–nano structures have been applied to fields such as photonic crystals, nonlinear optics, optical waveguides, and so on. At present, lithium niobate structural colors are rarely studied. Although the nanograting structure was researched, it [...] Read more.

Lithium niobate (LN) is a promising optical material, its micro–nano structures have been applied to fields such as photonic crystals, nonlinear optics, optical waveguides, and so on. At present, lithium niobate structural colors are rarely studied. Although the nanograting structure was researched, it has such large full width at half-maximum (fwhm) that it cannot achieve red, green, or blue pixels or other high-saturation structural colors, thus, its color printing quality is poor. In this paper, we design and simulate lithium niobate nanodisk metasurface resonators (LNNDMRs), which are based on Mie magnetic dipole (MD) and electric dipole (ED) resonances. In addition, the resonators yield very narrow reflection peaks and high reflection efficiencies with over 80%, especially the reflection peaks of red, green, and blue pixels with fwhm around 11 nm, 9 nm, and 6 nm, respectively. Moreover, output colors of different array cells composed of single nanodisk in finite size are displayed, which provides a theoretical basis for their practical applications. Therefore, LNNDMRs pave the way for high-efficiency, compact photonic display devices based on lithium niobate. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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7 pages, 1667 KiB

Open AccessArticle

Characteristics of a Source for Oxide Coating Deposition by the Electron-Beam Evaporation of Dielectric Materials

by Viktor Burdovitsin, Ilya Bakeev, Kirill Karpov, Lionel Ngon A. Kiki, Efim Oks and Alexey Vizir

Plasma 2022, 5(2), 258-264; https://doi.org/10.3390/plasma5020020 - 25 May 2022

Cited by 1 | Viewed by 2016

Abstract

We describe our investigations of a plasma-cathode electron source designed for the deposition of oxide coatings by the electron-beam evaporation of dielectric materials. Tests carried out using oxygen as the working gas showed that the source is operable without a change in parameters [...] Read more.

We describe our investigations of a plasma-cathode electron source designed for the deposition of oxide coatings by the electron-beam evaporation of dielectric materials. Tests carried out using oxygen as the working gas showed that the source is operable without a change in parameters for at least ten hours of continuous operation. The current–voltage characteristics of the hollow-cathode plasma source in oxygen displayed a monotonically increasing character, and the voltage dependence of the discharge current was exponential. At the same time, for argon, nitrogen, and helium, the discharge voltage remained unchanged over a current ranging from 0.1 A to 1 A. A possible reason for these differences is the formation of oxides on the electrode surfaces for operation in the oxygen, impeding the discharge operation and requiring higher voltages for the same current as the other gases. The dependencies of the electron beam current on the accelerating voltage were monotonically increasing curves for all the gases except for helium, for which the beam current remained unchanged with increasing voltage over a range from two to ten kilovolts. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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18 pages, 31230 KiB

Open AccessArticle

Optical Properties of Black Carbon Aerosols with Different Coating Models

by Yanxia Tang, Yong Huang and Keyong Zhu

Photonics 2022, 9(5), 359; https://doi.org/10.3390/photonics9050359 - 19 May 2022

Cited by 4 | Viewed by 2573

Abstract

Research on the optical properties of black carbon (BC) aerosols is highly important for investigating global climate change. A general inhomogeneous particle superposition model is developed. Inhomogeneous particles with arbitrary shapes can be constructed by this model. BC aerosols with core-shell, spherical, ellipsoid, [...] Read more.

Research on the optical properties of black carbon (BC) aerosols is highly important for investigating global climate change. A general inhomogeneous particle superposition model is developed. Inhomogeneous particles with arbitrary shapes can be constructed by this model. BC aerosols with core-shell, spherical, ellipsoid, and irregular coating models are established to explore the impact of coating shape on their optical properties. The optical properties are studied employing the discrete dipole approximation method (DDA). The influences of the morphology of BC aerosols, the coating volume fractions, and the shape of coatings on the optical properties are analyzed. The irregular coating shape causes a higher forward scattering intensity and a lower extinction cross-section. The forward scattering intensity of the core-shell model is lower than other models. The effect of the coating shape on forward scattering intensity becomes smaller as coating volume and fractal dimension increase. Consequently, assuming irregular coating as spherical coating models considered in most studies leads to inaccuracy in the optical properties of BC aerosols. It is necessary to comprehensively consider the effects of aerosol morphology and coating volume for investigating the optical properties of black carbon aerosols. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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7 pages, 1202 KiB

Open AccessCommunication

Spurious Tone Reduction and Signal Stabilization of Optoelectronic Oscillators by Low-Frequency RF Signal Modulation

by Jun-Hyung Cho, Hyo-Sang Jeong and Hyuk-Kee Sung

Photonics 2022, 9(5), 339; https://doi.org/10.3390/photonics9050339 - 12 May 2022

Cited by 1 | Viewed by 2434

Abstract

In this study, the oscillation signal stabilization and spurious tone suppression of a directly modulated optoelectronic oscillator (DM-OEO) are simultaneously achieved by modulating a laser with a low-frequency radio frequency (RF) signal. The laser in the DM-OEO is modulated by a rectangular wave [...] Read more.

In this study, the oscillation signal stabilization and spurious tone suppression of a directly modulated optoelectronic oscillator (DM-OEO) are simultaneously achieved by modulating a laser with a low-frequency radio frequency (RF) signal. The laser in the DM-OEO is modulated by a rectangular wave with a period inversely proportional to the frequency interval of the spurious tones and a duty cycle of 50%. The optical sidebands of the rectangular wave-modulated laser pulled the optical gain of the spurious tones of the DM-OEO, resulting in a spurious tone suppression and time stabilization in the DM-OEO signal. We achieve a 15 GHz DM-OEO with a 40.14 dB side-mode suppression ratio (SMSR) and 2.55 dB improvement in the oscillation power stability compared to that without RF modulation. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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