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Photonics
Volume 10
Issue 1
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Photonics, Volume 10, Issue 1 (January 2023) – 97 articles

Cover Story (view full-size image): Laser-driven ion acceleration is receiving particular attention for its important applications, such as hadron therapy, nuclear fusion, and use in material and nuclear physics. We reviewed our research in regimes dominated by radiation pressure acceleration with high-intensity laser irradiation of various targets relevant to laser centers such as ELI Beamlines. We demonstrated that a corrugation fabricated on the interface of double-layer targets leads to the generation of high-density and high-energy ion beams with low divergence. We proposed improvement of the ion acceleration with the laser pulse shaping via the shutter (a thin foil placed in front of the main target), generating a steep-front pulse with locally increased intensity. The results obtained with our simulations pave the way to building a new generation of laser-driven accelerators. View this paper
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18 pages, 342 KiB  
Editorial
Acknowledgment to the Reviewers of Photonics in 2022
by Photonics Editorial Office
Photonics 2023, 10(1), 97; https://doi.org/10.3390/photonics10010097 - 16 Jan 2023
Viewed by 2024
Abstract
High-quality academic publishing is built on rigorous peer review [...] Full article
17 pages, 5542 KiB  
Article
Removal Mechanisms and Microstructure Characteristics of Laser Paint Stripping on Aircraft Skin Surface
by Wenqin Li, Xuan Su, Junyi Gu, Yang Jin, Jie Xu and Bin Guo
Photonics 2023, 10(1), 96; https://doi.org/10.3390/photonics10010096 - 16 Jan 2023
Cited by 11 | Viewed by 3210
Abstract
As a non-contact and non-destructive technology, laser cleaning provides an alternative method for the paint stripping of aircraft skins. Herein, the particular multi-layer paint on the aluminum alloy aircraft skin surface was stripped by adjusting laser parameters. Beyond expectation, multi-layer paint led to [...] Read more.
As a non-contact and non-destructive technology, laser cleaning provides an alternative method for the paint stripping of aircraft skins. Herein, the particular multi-layer paint on the aluminum alloy aircraft skin surface was stripped by adjusting laser parameters. Beyond expectation, multi-layer paint led to a highly complex surface as opposed to the ordinary single-layer paint after laser cleaning. The surface morphology, chemical compositions, and surface functional groups of the samples were analyzed, and the successful depaint parameters were found in this experiment with damage free of the aluminum substrate, i.e., laser energy density of 5.09 J/cm2 and scanning speed of 700 mm/s. More importantly, this paper revealed that the mechanisms of laser paint stripping from Al alloy aircraft skin are thermal decomposition, evaporation, and spallation. After laser cleaning, the surface nanoindentation hardness with paint completely stripped and undamaged was increased by 3.587% relative to that of the conventional mechanical lapping sample. The improvement of nanoindentation hardness was also confirmed by the microstructure characterized with electron backscatter diffraction (EBSD) in which plastic deformation led to strain hardening of the substrate surface. This study lays a solid foundation for large-scale, high-efficiency, and low-pollution removal of more complex paint layers on aircraft surfaces in the future. Full article
(This article belongs to the Special Issue Ultrafast Laser Irradiation in Surface Engineering and Tribology)
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10 pages, 3124 KiB  
Communication
Compact and Low-Power-Consumption CO Sensor Using a QCL with Intermittent Scanning Technique
by Qinduan Zhang, Jie Hu, Yubin Wei, Binkai Li, Guancheng Liu, Tingting Zhang, Zhaowei Wang, Weihua Gong and Tongyu Liu
Photonics 2023, 10(1), 95; https://doi.org/10.3390/photonics10010095 - 15 Jan 2023
Viewed by 1946
Abstract
A compact and low-power-consumption gas sensor using a quantum cascade laser (QCL) emitting at 4.6 μm for measurement of carbon monoxide (CO) was proposed and experimentally demonstrated. A compact sensor structure with a physical dimension of 14 × 10 × 6.5 cm3 [...] Read more.
A compact and low-power-consumption gas sensor using a quantum cascade laser (QCL) emitting at 4.6 μm for measurement of carbon monoxide (CO) was proposed and experimentally demonstrated. A compact sensor structure with a physical dimension of 14 × 10 × 6.5 cm3 was designed. A new intermittent scanning technique was used to drive the QCL to reduce the power consumption of the system. In this technique, the power consumption of the sensor is as low as 1.08 W, which is about 75% lower than the conventional direct absorption technology. The stability of the CO sensor was demonstrated by continuously monitoring CO concentration for more than 1 h. In the concentration range of 10 ppm to 500 ppm, the CO sensor exhibited a satisfactory linear response (R-square = 0.9998). With an integration time of 202 s, the minimum detection limit was increased to 4.85 ppb, based on an Allan deviation analysis. Full article
(This article belongs to the Special Issue Emerging Frontiers in Photoacoustic Spectroscopy Detection)
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9 pages, 2966 KiB  
Communication
High-Speed Spiral-Phase Donut-Modes-Based Hybrid FSO-MMF Communication System by Incorporating OCDMA Scheme
by Meet Kumari, Abhishek Sharma and Sushank Chaudhary
Photonics 2023, 10(1), 94; https://doi.org/10.3390/photonics10010094 - 15 Jan 2023
Cited by 16 | Viewed by 1895
Abstract
Hybrid free-space optics (FSO) and optical fiber have been viewed as vital transmission techniques to satisfy high bandwidth and extended transmission range requirements under adverse environment conditions in the future last-mile obstruction problem. In this investigation, 80 Gbps data is transmitted on a [...] Read more.
Hybrid free-space optics (FSO) and optical fiber have been viewed as vital transmission techniques to satisfy high bandwidth and extended transmission range requirements under adverse environment conditions in the future last-mile obstruction problem. In this investigation, 80 Gbps data is transmitted on a hybrid FSO and multimode fiber (MMF)-based network using mode division multiplexing of two donut modes, Donut mode 0 and 1, and optical code-division multiplexing (OCDMA) schemes. For the OCDMA schemes, modified new zero-cross-correlation (MNZCC) codes are used, whereas, to add the phases into donut modes, a spiral phase diffuser is used. The purpose of the investigation is to provide an economical, high-speed and advanced last-mile network with adequate resource utilization for hybrid wired/wireless-based systems. The results obtained show achievement of an acceptable BER up to a fixed 100 m FSO link, with the combination of a 385 m MMF link under clear weather conditions. In another case, when the MMF link was fixed at 100 m, an acceptable bit error rate (BER) is achieved at 2.07 km FSO link. Furthermore, the results were obtained in the presence of strong and weak turbulences. A comparison of log-normal and gamma-gamma modeling for scintillations is presented. Full article
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13 pages, 1273 KiB  
Communication
Extended Representation of Mueller Matrices
by Ignacio San José and José J. Gil
Photonics 2023, 10(1), 93; https://doi.org/10.3390/photonics10010093 - 14 Jan 2023
Cited by 2 | Viewed by 2533
Abstract
The so-called arbitrary decomposition of a given Mueller matrix into a convex sum of nondepolarizing constituents provides a general framework for parallel decompositions of polarimetric interactions. Even though arbitrary decomposition can be performed through an infinite number of sets of components, the nature [...] Read more.
The so-called arbitrary decomposition of a given Mueller matrix into a convex sum of nondepolarizing constituents provides a general framework for parallel decompositions of polarimetric interactions. Even though arbitrary decomposition can be performed through an infinite number of sets of components, the nature of such components is subject to certain restrictions which limit the interpretation of the Mueller matrix in terms of simple configurations. In this communication, a new approach based on the addition of some portion of a perfect depolarizer before the parallel decomposition is introduced, leading to a set of three components which depend, respectively, on the first column, the first row, and the remaining 3 × 3 submatrix of the original Mueller matrix, so that those components inherit, in a decoupled manner, the polarizance vector, the diattenuation vector, and the combined complementary polarimetric information on depolarization and retardance. Full article
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13 pages, 4030 KiB  
Article
High-Sensitivity Temperature Sensor Based on the Perfect Metamaterial Absorber in the Terahertz Band
by Yan Wang, Yanqing Qiu, Yingping Zhang, Tingting Lang and Fengjie Zhu
Photonics 2023, 10(1), 92; https://doi.org/10.3390/photonics10010092 - 13 Jan 2023
Cited by 14 | Viewed by 2393
Abstract
In this study, a perfect metamaterial absorber (PMMA) based on an indium antimonide temperature-sensitive material is designed and investigated in the terahertz region. We demonstrate that it is an ideal perfect narrow-band absorber with polarization-insensitive and wide-angle absorption properties. Numerical simulation results show [...] Read more.
In this study, a perfect metamaterial absorber (PMMA) based on an indium antimonide temperature-sensitive material is designed and investigated in the terahertz region. We demonstrate that it is an ideal perfect narrow-band absorber with polarization-insensitive and wide-angle absorption properties. Numerical simulation results show that the proposed PMMA can be operated as a temperature sensor with a sensitivity of 21.9 GHz/K. A graphene layer was added to the PMMA structure to improve the sensitivity, and the temperature sensitivity was increased to 24.4 GHz/K. Owing to its excellent performance, the proposed PMMA can be applied in thermal sensing, detection, and switching. Full article
(This article belongs to the Special Issue Advanced Photonic Sensing and Measurement)
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11 pages, 4662 KiB  
Communication
Point-by-Point Induced High Birefringence Polymer Optical Fiber Bragg Grating for Strain Measurement
by Shixin Gao, Heng Wang, Yuhang Chen, Heming Wei, Getinet Woyessa, Ole Bang, Rui Min, Hang Qu, Christophe Caucheteur and Xuehao Hu
Photonics 2023, 10(1), 91; https://doi.org/10.3390/photonics10010091 - 13 Jan 2023
Cited by 5 | Viewed by 2077
Abstract
In this paper, the first- and fourth-order fiber Bragg grating (FBG)-based axial strain sensors are proposed. The FBGs are inscribed in step-index polymer optical fibers (POFs) (TOPAS core and ZEONEX cladding) via the point-by-point (PbP) direct-writing technique. A first-order FBG with a single [...] Read more.
In this paper, the first- and fourth-order fiber Bragg grating (FBG)-based axial strain sensors are proposed. The FBGs are inscribed in step-index polymer optical fibers (POFs) (TOPAS core and ZEONEX cladding) via the point-by-point (PbP) direct-writing technique. A first-order FBG with a single peak is obtained with a pulse fluence of 7.16 J/cm2, showing a strain sensitivity of 1.17 pm/με. After that, a fourth-order FBG with seven peaks is obtained with a pulse fluence of 1.81 J/cm2 with a strain sensitivity between 1.249 pm/με and 1.296 pm/με. With a higher fluence of 2.41 J/cm2, a second fourth-order FBG with five peaks is obtained, each of which is split into two peaks due to high birefringence (Hi-Bi) of ~5.4 × 10−4. The two split peaks present a strain sensitivity of ~1.44 pm/με and ~1.55 pm/με, respectively. The peak difference corresponding to Hi-Bi presents a strain sensitivity of ~0.11 pm/με and could potentially be used for simultaneous dual-parameter measurement, such as temperature and strain. Full article
(This article belongs to the Special Issue Direct Laser Writing for Photonic Applications)
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18 pages, 1280 KiB  
Article
Grant Report on the Transcranial near Infrared Radiation and Cerebral Blood Flow in Depression (TRIADE) Study
by Dan V. Iosifescu, Katherine A. Collins, Aura Hurtado-Puerto, Molly K. Irvin, Julie A. Clancy, Allison M. Sparpana, Elizabeth F. Sullivan, Zamfira Parincu, Eva-Maria Ratai, Christopher J. Funes, Akila Weerasekera, Jacek P. Dmochowski and Paolo Cassano
Photonics 2023, 10(1), 90; https://doi.org/10.3390/photonics10010090 - 13 Jan 2023
Cited by 4 | Viewed by 3849
Abstract
We report on the rationale and design of an ongoing National Institute of Mental Health (NIMH) sponsored R61-R33 project in major depressive disorder (MDD). Current treatments for MDD have significant limitations in efficacy and side effect burden. There is a critical need for [...] Read more.
We report on the rationale and design of an ongoing National Institute of Mental Health (NIMH) sponsored R61-R33 project in major depressive disorder (MDD). Current treatments for MDD have significant limitations in efficacy and side effect burden. There is a critical need for device-based treatments in MDD that are efficacious, well-tolerated, and easy to use. This project focuses on the adjunctive use of the transcranial photobiomodulation (tPBM) with near-infrared (NIR) light for the treatment of MDD. tPBM with NIR light penetrates robustly into the cerebral cortex, stimulating the mitochondrial respiratory chain, and also significantly increases cerebral blood flow (CBF). In the R61 phase, we will conduct target engagement studies to demonstrate dose-dependent effects of tPBM on the prefrontal cortex (PFC) CBF, using the increase in fMRI blood-oxygenation-level-dependent (BOLD) signal levels as our Go/No-go target engagement biomarker. In the R33 phase, we will conduct a randomized clinical trial of tPBM vs. sham in MDD to establish the target engagement and evaluate the association between changes in the biomarker (BOLD signal) and changes in clinical symptoms, while also collecting important information on antidepressant effects, safety, and tolerability. The study will be done in parallel at New York University/the Nathan Kline Institute (NYU/NKI) and at Massachusetts General Hospital (MGH). The importance of this study is threefold: 1. it targets MDD, a leading cause of disability worldwide, which lacks adequate treatments; 2. it evaluates tPBM, which has a well-established safety profile and has the potential to be safe in at-home administration; and 3. it uses fMRI BOLD changes as a target engagement biomarker. If effects are confirmed, the present study will both support short-term clinical development of an easy to scale device for the treatment of MDD, while also validating a biomarker for the development of future, novel modulation strategies. Full article
(This article belongs to the Section Biophotonics and Biomedical Optics)
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14 pages, 7264 KiB  
Article
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 1790
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 (TE, [s]), laser beam power (P, [W]) and number of pulses (NP) on resulting geometrical features, namely, crack length (CL, [mm]), inlet diameter (DINLET, [mm]) and exit diameter (DEXIT, [mm]). The processed samples were characterized using an optical microscope. Findings show that LALP with investigated ranges of control parameters TE (0.5–1.5 s), P (20–40 W) and NP (1–6 pulses) led to successful production of drilled holes having CL range (0.141 to 0.428 mm), DINLET range (0.406 to 1.452 mm) and DEXIT range (0.247 to 1.039 mm). It was concluded that increasing TE alone leads to increasing CL, DINLET and DEXIT, while keeping a good balance among the control parameters, especially TE and NP, 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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3 pages, 172 KiB  
Editorial
Special Issue on Optical Quantum Manipulation of Rydberg Atoms
by Dong Yan and Jin-Hui Wu
Photonics 2023, 10(1), 88; https://doi.org/10.3390/photonics10010088 - 13 Jan 2023
Viewed by 1398
Abstract
Rydberg atoms with large electric dipole moments, strong dipole–dipole interactions, and long radiative lifetimes have attracted great attention and become the subject of intense studies in the past two decades [...] Full article
(This article belongs to the Special Issue Optical Quantum Manipulation of Rydberg Atoms)
8 pages, 1494 KiB  
Communication
Design and Theoretical Investigation of an on Chip Two-Dimensional Newton’s Ring-like Plasmonic Sensor for Differentiating the Chirality of Circularly Polarized Lights
by Lina Zhang, Chunyan Bai, Yan Xu, Tao Pang, Xufeng Zang, Dakui Zeng and Peizhen Qiu
Photonics 2023, 10(1), 87; https://doi.org/10.3390/photonics10010087 - 12 Jan 2023
Viewed by 1444
Abstract
In this paper, an on chip two-dimensional Newton’s ring-like plasmonic sensor is designed for differentiating the chirality of circularly polarized lights (CPLS). The structure of the plasmonic sensor consists of a circular arc slit and an array of periodic rectangular nano-grooves that are [...] Read more.
In this paper, an on chip two-dimensional Newton’s ring-like plasmonic sensor is designed for differentiating the chirality of circularly polarized lights (CPLS). The structure of the plasmonic sensor consists of a circular arc slit and an array of periodic rectangular nano-grooves that are etched into a silver film. When the sensor is illuminated by CPLS with a given chirality, the surface plasmon polariton waves generated by the slit and nano-groove array will selectively interfere with each other in the near field, which results in two different transmitted light intensity distributions in the far field. The generated far-field light intensity distributions are utilized as criteria to qualitatively differentiate the concrete chirality of the incident CPLS. The finite difference time domain method is utilized to theoretically investigate the function of the designed plasmonic sensor. The simulated results indicated that the proposed sensor has the ability to visually display the chirality information in the far field, and can provide a tool to conveniently and qualitatively differentiate the chirality of CPLS in the far field. Full article
(This article belongs to the Special Issue Surface Plasmon)
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11 pages, 1536 KiB  
Article
Photostress Recovery Time after Flash-Lighting Is Increased in Myopic Eyes
by Francisco J. Ávila, Pilar Casado and Jorge Ares
Photonics 2023, 10(1), 86; https://doi.org/10.3390/photonics10010086 - 12 Jan 2023
Cited by 1 | Viewed by 2994
Abstract
Background: It is well-known that non-pathological axial myopic eyes present physiological and functional differences in comparison with emmetropic eyes due to altered retinal anatomy. Photostress tests have shown very significant capabilities to discriminate a normal retina from an abnormal retina. Accordingly, the aim [...] Read more.
Background: It is well-known that non-pathological axial myopic eyes present physiological and functional differences in comparison with emmetropic eyes due to altered retinal anatomy. Photostress tests have shown very significant capabilities to discriminate a normal retina from an abnormal retina. Accordingly, the aim of this work was to investigate the differences between myopic and emmetropic eyes in the measured photostress recovery time (PSRT) after retinal light-flashing in a population of young healthy subjects. Methods: A coaxial illumination total disability glare instrument was employed to measure the recovery time after photostress was induced by a 240 milliseconds flash-lighting (535 nm) exposure on 66 myopic and 66 emmetropic eyes. The measurements were carried out for different combinations of glare angles and contrasts of the visual stimuli. Results: In general terms, PSRT in myopic eyes was found at a statistically higher than in emmetropic eyes (Bonferroni correction). For both groups, the measured recovery strongly depends on the contrast of the test object used to measure baseline recovery function and markedly less on the source of glare angles explored. When the PSRTs obtained for different glare angles are averaged, the differences between PSRTs drastically increase with the reduction in the contrast of the stimuli between both groups of study. Conclusions: PSRT is higher for myopic than for young healthy emmetropic eyes (1.2 s and 0.2 s for 5% and 100% contrast test object, respectively). Though seemingly small, the magnitude of this finding can be relevant when flash-lighting happens while driving a car or while performing actions where the reaction time after a visual stimulus can be critical. Full article
(This article belongs to the Special Issue Visual Optics)
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8 pages, 2836 KiB  
Communication
Ultra-Broadband NPE-Based Femtosecond Fiber Laser
by Sergei I. Abdrakhmanov, Vladislav D. Efremov, Alexey G. Kuznetsov, Denis S. Kharenko and Sergey A. Babin
Photonics 2023, 10(1), 85; https://doi.org/10.3390/photonics10010085 - 12 Jan 2023
Viewed by 2029
Abstract
A dissipative soliton mode-locked Yb-doped fiber laser is investigated experimentally and numerically from the point of view of generating ultra-broadband ultrashort pulses. An energy up to 2.2 nJ and a spectral bandwidth over 60 nm (at the −10 dB level) were obtained experimentally [...] Read more.
A dissipative soliton mode-locked Yb-doped fiber laser is investigated experimentally and numerically from the point of view of generating ultra-broadband ultrashort pulses. An energy up to 2.2 nJ and a spectral bandwidth over 60 nm (at the −10 dB level) were obtained experimentally without dispersion compensation in the cavity. Almost a 100-fold compression coefficient has been achieved, so the resulting pulse duration was 149 fs. The numerical simulation has shown that a further scaling up to 3.5 nJ and a 100 nm spectral bandwidth is possible by reducing the low power transmission coefficient of the NPE-based SAM and increasing the amplification. At the same time, the tolerance of the SAM to a low power radiation is responsible for the transition to a multi-pulse operation regime. Full article
(This article belongs to the Special Issue High Power Laser: Theory and Applications)
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11 pages, 16353 KiB  
Article
Optical Properties of LiGdF4 Single Crystal in the Terahertz and Infrared Ranges
by Gennady A. Komandin, Sergey P. Lebedev, Stella L. Korableva, Oleg A. Morozov, Vladimir M. Kyashkin, Vadim V. Semashko and Pavel P. Fedorov
Photonics 2023, 10(1), 84; https://doi.org/10.3390/photonics10010084 - 11 Jan 2023
Cited by 2 | Viewed by 1867
Abstract
The basic mechanisms of absorption of THz range radiation in optically perfect LiGdF4 single crystals were studied using the broadband experimental data and the dielectric response function analysis within the harmonic oscillator model. The polarized IR reflection spectra have allowed one to [...] Read more.
The basic mechanisms of absorption of THz range radiation in optically perfect LiGdF4 single crystals were studied using the broadband experimental data and the dielectric response function analysis within the harmonic oscillator model. The polarized IR reflection spectra have allowed one to determine the phonon contribution in the absorption coefficient in the THz range, while transmission spectra in the THz range were used to obtain the birefringence value and the effects of various mulitparticle processes. Additionally, we established the optical and electrodynamic parameters of the LiGdF4 single crystal, which are necessary for the design of nonlinear optical devices. Full article
(This article belongs to the Special Issue Terahertz Spectroscopy and Imaging)
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10 pages, 3745 KiB  
Communication
Study of Straight-Line-Type Sagnac Optical Fiber Acoustic Sensing System
by Jiang Wang, Ruixi Tang, Jianjun Chen, Ning Wang, Yong Zhu, Jie Zhang and Juan Ruan
Photonics 2023, 10(1), 83; https://doi.org/10.3390/photonics10010083 - 11 Jan 2023
Cited by 6 | Viewed by 1642
Abstract
A straight-line-type Sagnac optic fiber acoustic sensing system is proposed in this paper to adopt the application needs of no man’s plateau borderline for monitoring mechanical invasion. The Sagnac interference fiber loop is replaced by a straight-line fiber and a 1 × 2 [...] Read more.
A straight-line-type Sagnac optic fiber acoustic sensing system is proposed in this paper to adopt the application needs of no man’s plateau borderline for monitoring mechanical invasion. The Sagnac interference fiber loop is replaced by a straight-line fiber and a 1 × 2 coupler, and the length of the Sagnac interference fiber loop is shortened by close to 50%. The influences of delay fiber and sensing fiber on the sensing system are analyzed by theory calculation and simulation and the optimal lengths of delay fiber and sensing fiber were decided. The experiment system was set, and the sensing fiber was wound into titanium alloy cylinder to compose the sensing element. Experimental results show that the sensing system has a good response to 50−8000 Hz and 70 dB sinusoidal acoustical signals and can well distinguish the signals of different frequencies. Using a small-scale helicopter audio signal as the acoustical signal, the test results show that the response curve is consistent with the simulation results and the sensitivity reaches 30.67 mV/Pa. Full article
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15 pages, 3492 KiB  
Article
Highly Sensitive Multichannel Fano Resonance-Based Plasmonic Sensor for Refractive Index and Temperature Sensing Application
by Chung-Ting Chou Chao and Yuan-Fong Chou Chau
Photonics 2023, 10(1), 82; https://doi.org/10.3390/photonics10010082 - 11 Jan 2023
Cited by 18 | Viewed by 2653
Abstract
We propose a susceptible multichannel plasmonic sensor for sensing refractive index (RI) and temperature media working in the visible to near-infrared range. The proposed structure’s resonator consists of an elliptical-shaped ring with two stubs at two sides and four metal nanorods side-coupled to [...] Read more.
We propose a susceptible multichannel plasmonic sensor for sensing refractive index (RI) and temperature media working in the visible to near-infrared range. The proposed structure’s resonator consists of an elliptical-shaped ring with two stubs at two sides and four metal nanorods side-coupled to two separated metal–insulator–metal waveguides. The optical responses of the structure, including transmittance spectra and magnetic and electric field distributions, are investigated using the finite element method (FEM) to obtain the optimal structural parameters. The designed structure supports five channels of Fano resonance modes because of the interaction between the narrowband mode of the elliptical-shaped ring resonator and the broadband mode of two separated MIM WGs. The maximum sensitivity values can reach 4500 nm/RIU for RI sensing, and the temperature sensitivity can get 1.00 nm/°C. The designed device exhibits excellent sensing performance and could pave the way for sensing devices with significantly higher sensitivity. Full article
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8 pages, 2913 KiB  
Communication
1.73 kW CW Amplification ASE Source Based on Yb3+ Ions-Doped All-Fiber System
by Xin Li, Zhe Zhang, Xinyang Xu, Junjie Liu and Xiaolei Bai
Photonics 2023, 10(1), 81; https://doi.org/10.3390/photonics10010081 - 10 Jan 2023
Viewed by 1755
Abstract
The all-fiber ASE source is an intriguing tool in the fields of super-fluorescence detection, coherent measurement and spectrum analysis technology. We experimentally demonstrate a continuous all-fiber amplified spontaneous emission (ASE) source based on amaster-oscillator power amplifier (MOPA) system, which aims at achieving high [...] Read more.
The all-fiber ASE source is an intriguing tool in the fields of super-fluorescence detection, coherent measurement and spectrum analysis technology. We experimentally demonstrate a continuous all-fiber amplified spontaneous emission (ASE) source based on amaster-oscillator power amplifier (MOPA) system, which aims at achieving high power and frequency stability. The seed source is homemade ASE low power super-fluorescence source with 200 mW. The system employs large-mode-area Yb3+-doped double-clad fiber (LMA-DCF), and the maximum power can reach 1.73 kW at a center wavelength of 1079.36 nm, and can maintain an optical-to-optical conversion efficiency of 79.13%. During 30 min of real-time monitoring, the ASE source system did not generate a nonlinear effect, and power fluctuation was less than 2%. Full article
(This article belongs to the Special Issue Fiber Optics and Its Applications)
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8 pages, 1633 KiB  
Communication
Broadband Second Harmonic Generation in a z-Cut Lithium Niobate on Insulator Waveguide Based on Type-I Modal Phase Matching
by Changwen Wang, Haozong Zhong, Minghao Ning, Bin Fang, Lin Li and Ya Cheng
Photonics 2023, 10(1), 80; https://doi.org/10.3390/photonics10010080 - 10 Jan 2023
Cited by 10 | Viewed by 3181
Abstract
We numerically investigate a second harmonic generation (SHG) in a z-cut lithium niobate on insulator (LNOI) waveguide based on type-I mode phase matching (MPM) between two fundamental modes. A mode overlap factor that is close to unity is achieved and the normalized SHG [...] Read more.
We numerically investigate a second harmonic generation (SHG) in a z-cut lithium niobate on insulator (LNOI) waveguide based on type-I mode phase matching (MPM) between two fundamental modes. A mode overlap factor that is close to unity is achieved and the normalized SHG efficiency reaches up to 72.1% W−1cm−2 at the telecommunication band, together with a large spectral tunability of 2.5 nm/K. Moreover, a bandwidth of about 100 nm for the broad SHG in a 5 mm-long LNOI ridge waveguide is demonstrated with this scheme. This stratagem will inspire new integrated nonlinear frequency conversion methods for versatile applications. Full article
(This article belongs to the Special Issue Photonic Crystals: Physics and Devices)
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17 pages, 6093 KiB  
Article
Enhanced Performance of a Cascaded Receiver Consisting of a DNN-Based Waveform-to-Symbol Converter and Modified NN-Based DD-LMS in CAP Underwater VLC System
by Xianhao Lin, Fangchen Hu and Nan Chi
Photonics 2023, 10(1), 79; https://doi.org/10.3390/photonics10010079 - 10 Jan 2023
Cited by 5 | Viewed by 3905
Abstract
Underwater visible light communication (UVLC) based on LEDs has become a competitive candidate, which is able to provide high data rates, low latency and low cost for next-generation wireless communication technologies. However, it is still challenging to achieve high-speed communication because of bottleneck [...] Read more.
Underwater visible light communication (UVLC) based on LEDs has become a competitive candidate, which is able to provide high data rates, low latency and low cost for next-generation wireless communication technologies. However, it is still challenging to achieve high-speed communication because of bottleneck problems such as bandwidth limitation and linear and nonlinear distortions. Traditional Deep-learning Neural Network (DNN)-based waveform-to-symbol converter is verified to be an effective method to alleviate them, but impractical due to high complexity. To achieve a better tradeoff between communication performance and computation complexity, a cascaded receiver consisting of a DNN-based waveform-to-symbol converter and modified Neural Network (NN)-based decision-directed least mean square (DD-LMS) is then innovatively proposed. With fewer taps and nodes than the traditional converter, the front-stage converter could mitigate the majority of Inter-Symbol Interference (ISI) and signal nonlinear distortions. Then modified NN-based DD-LMS is cascaded to improve communication performance by reducing phase offset, making received constellation points more concentrated and closer to standard constellation points. Compared with the traditional converter, the cascaded receiver could achieve 89.6% of signal Vpp dynamic range with 12.4% of complexity in the 64APSK UVLC system. Moreover, the ratio of signal Vpp dynamic range and total trainable parameters is 1.24 × 10−1 mV, while that of the traditional converter is 1.95 × 10−2 mV. The cascaded receiver used in 64APSK UVLC systems is experimentally verified to achieve enhanced performance, thus as a promising scheme for future high-speed underwater VLC. Full article
(This article belongs to the Special Issue Visible Light Communications)
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12 pages, 3701 KiB  
Article
Plasmonic Properties of the Metal Nanoparticles (NPs) on a Metal Mirror Separated by an Ultrathin Oxide Layer
by Niloofar Ebrahimzadeh Esfahani, Jaroslav Kováč, Jr., Soňa Kováčová and Martin Feiler
Photonics 2023, 10(1), 78; https://doi.org/10.3390/photonics10010078 - 10 Jan 2023
Cited by 3 | Viewed by 2524
Abstract
The plasmonic resonance frequency of metal nanoparticles (NPs) strongly depend on the geometry, size, and separation between NPs. Here, a plasmonic structure is designed based on a film-coupled nanoparticle phenomenon and analytically investigated by a finite element method via COMSOL Multiphysics software tool. [...] Read more.
The plasmonic resonance frequency of metal nanoparticles (NPs) strongly depend on the geometry, size, and separation between NPs. Here, a plasmonic structure is designed based on a film-coupled nanoparticle phenomenon and analytically investigated by a finite element method via COMSOL Multiphysics software tool. The optical behavior of the designed structure is studied and compared for two noble metals (gold and silver as a case study). Simulation results confirmed that structural elements such as dielectric layer thickness, metal film thickness, and metal nanoparticle separation distance significantly affect the plasmonic properties. Consequently, optimizing the dimensions of the mentioned structural elements results in a strong field enhancement in the dielectric gap layer. The simplicity of this structure, easy controlling of the dielectric gap layer thickness, strong field confinement in a limited area, and lack of incident light angle tunning are characteristic features of the proposed structure. Strong field enhancement in a limited volume makes this structure promising as plasmonic nanoantennas, SERS platforms, and sensing applications. Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
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7 pages, 1587 KiB  
Communication
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 2068
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  
Article
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 1578
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 2ω=ω+ω and 3ω=2ω+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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10 pages, 1110 KiB  
Communication
Diamond Photoconductive Antenna for Terahertz Generation Equipped with Buried Graphite Electrodes
by Taras Viktorovich Kononenko, Kuralai Khamitzhanovna Ashikkalieva, Vitali Viktorovich Kononenko, Evgeny Viktorovich Zavedeev, Margarita Alexandrovna Dezhkina, Maxim Sergeevich Komlenok, Evgeny Evseevich Ashkinazi, Vladimir Valentinovich Bukin and Vitaly Ivanovich Konov
Photonics 2023, 10(1), 75; https://doi.org/10.3390/photonics10010075 - 9 Jan 2023
Cited by 4 | Viewed by 2005
Abstract
It has been shown recently that a photoconductive antenna (PCA) based on a nitrogen-doped diamond can be effectively excited by the second harmonic of a Ti:sapphire laser (λ = 400 nm). The THz emission performance of the PCA can be significantly increased if [...] Read more.
It has been shown recently that a photoconductive antenna (PCA) based on a nitrogen-doped diamond can be effectively excited by the second harmonic of a Ti:sapphire laser (λ = 400 nm). The THz emission performance of the PCA can be significantly increased if a much stronger electric field is created between the close-located electrodes. To produce a homogeneous electric field over the entire excited diamond volume, the laser fabrication of deep-buried graphite electrodes inside the diamond crystal was proposed. Several electrodes consisting of the arrays of buried pillars connected by the surface graphite stripes were produced inside an HPHT diamond crystal using femtosecond and nanosecond laser pulses. Combining different pairs of the electrodes, a series of PCAs with various electrode interspaces was formed. The THz emission of the PCAs equipped with the buried electrodes was measured at different values of excitation fluence and bias voltage (DC and pulsed) and compared with the emission of the same diamond crystal when the bias voltage was applied to the surface electrodes on the opposite faces. All examined PCAs have demonstrated the square-law dependencies of the THz fluence on the field strength, while the saturation fluence fluctuated in the range of 1200–1600 µJ/cm2. The THz emission performance was found to be approximately the same for the PCAs with the surface electrodes and with the buried electrodes spaced at a distance of 1.4–3.5 mm. However, it noticeably decreased when the distance between the buried electrodes was reduced to 0.5 mm. Full article
(This article belongs to the Special Issue THz Imaging and Spectroscopy)
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9 pages, 1413 KiB  
Communication
An All Optical 2 × 1 Multiplexer Using a Metal-Insulator-Metal based Plasmonic Waveguide for Processing at a Rapid Pace
by Ipshitha Charles, Sandip Swarnakar, Geetha Rani Nalubolu, Venkatrao Palacharla and Santosh Kumar
Photonics 2023, 10(1), 74; https://doi.org/10.3390/photonics10010074 - 9 Jan 2023
Cited by 5 | Viewed by 1957
Abstract
This study proposes, designs, and simulates a unique plasmonic Y-shaped MIM waveguide based 2 × 1 multiplexer (MUX) structure utilising opti-FDTD software. Two plasmonic Y-shaped waveguides are positioned facing one another inside a minimum wafer size of 6 µm × 3.5 µm in [...] Read more.
This study proposes, designs, and simulates a unique plasmonic Y-shaped MIM waveguide based 2 × 1 multiplexer (MUX) structure utilising opti-FDTD software. Two plasmonic Y-shaped waveguides are positioned facing one another inside a minimum wafer size of 6 µm × 3.5 µm in the 2 × 1 MUX configurations that is being described. The design parameters are adjusted until the plasmonic multiplexer performs as required under optimal conditions. Extinction ratio and insertion loss are two performance metrics that are calculated for performance analysis of the design, which indicate the potential to be applied in plasmonic integrated circuits. Full article
(This article belongs to the Special Issue Optical Signal Processing)
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15 pages, 3047 KiB  
Article
EA-UNet Based Segmentation Method for OCT Image of Uterine Cavity
by Zhang Xiao, Meng Du, Junjie Liu, Erjie Sun, Jinke Zhang, Xiaojing Gong and Zhiyi Chen
Photonics 2023, 10(1), 73; https://doi.org/10.3390/photonics10010073 - 9 Jan 2023
Cited by 5 | Viewed by 2429
Abstract
Optical coherence tomography (OCT) image processing can provide information about the uterine cavity structure, such as endometrial surface roughness, which is important for the diagnosis of uterine cavity lesions. The accurate segmentation of uterine cavity OCT images is a key step of OCT [...] Read more.
Optical coherence tomography (OCT) image processing can provide information about the uterine cavity structure, such as endometrial surface roughness, which is important for the diagnosis of uterine cavity lesions. The accurate segmentation of uterine cavity OCT images is a key step of OCT image processing. We proposed an EA-UNet-based image segmentation model that uses a U-Net network structure with a multi-scale attention mechanism to improve the segmentation accuracy of uterine cavity OCT images. The E(ECA-C) module introduces a convolutional layer combined with the ECA attention mechanism instead of max pool, reduces the loss of feature information, enables the model to focus on features in the region to be segmented, and suppresses irrelevant features to enhance the network’s feature-extraction capability and learning potential. We also introduce the A (Attention Gates) module to improve the model’s segmentation accuracy by using global contextual information. Our experimental results show that the proposed EA-UNet can enhance the model’s feature-extraction ability; furthermore, its MIoU, Sensitivity, and Specificity indexes are 0.9379, 0.9457, and 0.9908, respectively, indicating that the model can effectively improve uterine cavity OCT image segmentation and has better segmentation performance. Full article
(This article belongs to the Section Biophotonics and Biomedical Optics)
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9 pages, 396 KiB  
Communication
Optimal Measurement of Telecom Wavelength Single Photon Polarisation via Hong-Ou-Mandel Interferometry
by Fabrizio Sgobba, Deborah Katia Pallotti, Arianna Elefante, Stefano Dello Russo, Daniele Dequal, Mario Siciliani de Cumis and Luigi Santamaria Amato
Photonics 2023, 10(1), 72; https://doi.org/10.3390/photonics10010072 - 9 Jan 2023
Cited by 5 | Viewed by 1743
Abstract
The use of statistical estimation theory to boost the metrological performance of the measurement apparatus is becoming increasingly popular in a wide range of applications. Recently, such an approach has been adopted in Hong Ou Mandel interferometry, setting a new record in time [...] Read more.
The use of statistical estimation theory to boost the metrological performance of the measurement apparatus is becoming increasingly popular in a wide range of applications. Recently, such an approach has been adopted in Hong Ou Mandel interferometry, setting a new record in time delay and polarization measurement. Here, we extend these pioneering experiments in the telecom range to unlock the full potential of the information-based approach combined with a versatile spectral range, aiming for its adoption in fiber-coupled devices of up to hundreds of kilometers long as bobines or optical networks. Our measurement saturates the Cramér-Rao bound and in a long lasting experiment returns an Allan deviation of the polarization angle of 0.002 degs in 1 h of integration time. Full article
(This article belongs to the Section Quantum Photonics and Technologies)
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11 pages, 586 KiB  
Communication
Photonic Crystal-Based Water Concentration Estimation in Blood Using Machine Learning for Identification of the Haematological Disorder
by Ankit Agarwal, Nitesh Mudgal, Kamal Kishor Choure, Rahul Pandey, Ghanshyam Singh and Satish Kumar Bhatnagar
Photonics 2023, 10(1), 71; https://doi.org/10.3390/photonics10010071 - 9 Jan 2023
Cited by 3 | Viewed by 2245
Abstract
Human blood is made up primarily of water. Water is significantly involved in balancing the human body. It affects the component of blood like mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and mean platelets volume (MPV). The water concentration varies from [...] Read more.
Human blood is made up primarily of water. Water is significantly involved in balancing the human body. It affects the component of blood like mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and mean platelets volume (MPV). The water concentration varies from 80 to 90% in blood. The change in water concentration changes the refractive index of plasma, and the change in the refractive index of plasma also changes the refractive index of blood. The proposed structure is designed to analyze the water concentration in human blood by analyzing the shifting in resonant peak and this shifting is processed by machine learning algorithm to estimate the concentration of water in human blood. Nanocavity ring structures in the waveguide region are designed as sensing nodes in this proposed structure. The air hole radius of these Nanocavity ring structures is 80 and 50 nm, whereas the proposed structure’s dimension is 12.15 by 8.45 μm2. The sensitivity of the design structure is 570 nm/RIU, and the quality factor is 650. The structure is simulated through the Finite Difference Time Domain (FDTD) method. Full article
(This article belongs to the Special Issue Optical Machine Learning for Communication and Networking)
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15 pages, 6129 KiB  
Article
Structural Color of Multi-Order Fabry–Perot Resonator Based on Sc0.2Sb2Te3 Enhanced Saturated Reflection Color
by Yangbo Lian, Yongzhi Zhang, Furong Liu, Qingyuan Chen, Lulu Zhang and Boshuo Yin
Photonics 2023, 10(1), 70; https://doi.org/10.3390/photonics10010070 - 9 Jan 2023
Cited by 2 | Viewed by 1846
Abstract
The structural color based on the Fabry–Perot (F–P) resonator has been extensively applied lithography-free and tunable color displays. Conventional F–P cavity-based structural color technology exhibits a wide half maximum full width (fwhm), thus causing low color saturation. In this study, a Sc0.2 [...] Read more.
The structural color based on the Fabry–Perot (F–P) resonator has been extensively applied lithography-free and tunable color displays. Conventional F–P cavity-based structural color technology exhibits a wide half maximum full width (fwhm), thus causing low color saturation. In this study, a Sc0.2Sb2Te3(SST) based structure of multi-order F–P cavity resonance was proposed to obtain high-saturation colors. The surface absorber of the multi-order F–P resonator structure was coated with an SST film, such that the reflection effect at nonresonant wavelengths was reduced. Moreover, ITO layer stacking served as F–P cavity resonance for multi-level modulation, and only a resonant wavelength was allowed to reflect. On that basis, the fwhm of nearly 25 nm and a peak reflectance of 90 was achieved. With the above structure, the color saturation can be dynamically regulated by the phase state of the SST. It is noteworthy that 60% sRGB color gamut space and 50% aRGB color gamut space can be currently achieved. The proposed modulation subsurface is expected to expand the color range of high-level and micro-nano display technology. Full article
(This article belongs to the Special Issue Micro-Nano Optical Devices)
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9 pages, 1907 KiB  
Communication
Research on A High-Sensitivity Temperature Sensor with Multi-Indicator Based on Nano-Cylinder-Loaded Ring Resonator
by Peng Zhou, Kun Liang, Yilin Wang, Qing’an Sun, Jiaqi Guo, Lei Jin and Li Yu
Photonics 2023, 10(1), 69; https://doi.org/10.3390/photonics10010069 - 8 Jan 2023
Cited by 6 | Viewed by 1837
Abstract
Increasing sensor sensitivity and maintaining a large FOM (figure of merit) are challenging to achieve at the same time. Adding grooves and asymmetrical structures to the annular cavity increases sensitivity; however, it usually makes the FOM of the structure decrease. Herein, we propose [...] Read more.
Increasing sensor sensitivity and maintaining a large FOM (figure of merit) are challenging to achieve at the same time. Adding grooves and asymmetrical structures to the annular cavity increases sensitivity; however, it usually makes the FOM of the structure decrease. Herein, we propose a MIM (metal-insulator-metal) sensor of a novel structure with nano-cylinders loaded in a ring resonator (NCRR), whose sensitivity can reach as high as 3636.4 nm/RIU (refractive index unit). The FOM is maintained around 2000 in the mid-infrared (MIR) region. We find that grating effects only occur in the ring cavity when the cylinder’s distance is below three times its radius, and it can improve the sensitivity of the proposed structure up to 42.3% without decreasing its FOM. In addition, results suggest that our sensor has excellent resistance to eccentricity, which brings in manufacturing. Furthermore, we investigate the capability of the proposed device as a temperature sensor with ethanol, which exhibits a maximum temperature sensitivity of 1.48 nm/°C. We believe that our research has essential application prospects in miniature integrated sensors, optical switches, splitters, filters, and broadband passers. Full article
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21 pages, 5501 KiB  
Article
Highly Sensitive Bilirubin Biosensor Based on Photonic Crystal Fiber in Terahertz Region
by Ahmed Refaat Elhelw, Mahmoud Salman S. Ibrahim, Ahmed Nabih Zaki Rashed, Abd El-Naser A. Mohamed, Mohamed Farhat O. Hameed and Salah S. A. Obayya
Photonics 2023, 10(1), 68; https://doi.org/10.3390/photonics10010068 - 8 Jan 2023
Cited by 17 | Viewed by 2501
Abstract
An unstable bilirubin level in the human blood causes many dangerous health problems, such as jaundice, coronary artery disease, ulcerative colitis, and brain lesions. Therefore, the accurate and early detection of bilirubin concentrations in the blood is mandatory. In this work, a highly [...] Read more.
An unstable bilirubin level in the human blood causes many dangerous health problems, such as jaundice, coronary artery disease, ulcerative colitis, and brain lesions. Therefore, the accurate and early detection of bilirubin concentrations in the blood is mandatory. In this work, a highly sensitive biosensor based on photonic crystal fiber (PCF) for monitoring bilirubin levels is proposed and analyzed. The sensor parameters, including relative sensitivity, effective mode area, confinement loss, and effective material loss, are calculated. The geometrical parameters are studied, and a modal analysis of the suggested sensor is carried out using the full-vectorial finite element method (FEM). The fabrication tolerance of the geometrical parameters is also studied to ensure the fabrication feasibility of the reported design. High sensitivities of 95% and 98% are obtained for the x-polarized and y-polarized modes, respectively. Furthermore, a small material loss of 0.00193 cm−1, a small confinement loss of 2.03 × 10−14 dB/cm, and a large effective mode area of 0.046 mm2 are achieved for the y-polarized mode. It is believed that the presented sensor will be helpful in health care and in the early detection of bilirubin levels in the blood. Full article
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