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12 pages, 5876 KiB

Open AccessEditor’s ChoiceArticle

Online Denoising Single-Pixel Imaging Using Filtered Patterns

by Zhaohua Yang, Xiang Chen, Zhihao Zhao, Lingan Wu and Yuanjin Yu

Photonics 2024, 11(1), 59; https://doi.org/10.3390/photonics11010059 - 5 Jan 2024

Cited by 1 | Viewed by 1293

Abstract

Noise is inevitable in single-pixel imaging (SPI). Although post-processing algorithms can significantly improve image quality, they introduce additional processing time. To address this issue, we propose an online denoising single-pixel imaging scheme at the sampling stage, which uses the filter to optimize the [...] Read more.

Noise is inevitable in single-pixel imaging (SPI). Although post-processing algorithms can significantly improve image quality, they introduce additional processing time. To address this issue, we propose an online denoising single-pixel imaging scheme at the sampling stage, which uses the filter to optimize the illumination modulation patterns. The image is retrieved through the second-order correlation between the modulation patterns and the intensities detected by the single-pixel detector. Through simulations and experiments, we analyzed the impact of sampling rate, noise intensity, and filter template on the reconstructed images of both binary and grayscale objects. The results demonstrate that the denoising effect is comparable to the imaging-first followed by post-filtering procedures, but the post-processing time is reduced for the same image quality. This method offers a new way for rapid denoising in SPI, and it should be particularly advantageous in applications where time-saving is of paramount importance, such as in image-free large target classification. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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15 pages, 4716 KiB

Open AccessArticle

Active Differential Fiber Coupled Plasmon Waveguide Resonance Sensor Based on the Mode Competition Effect

by Songquan Li, Qian Yang, Laixu Gao, Miao Zhu and Changwei Zou

Photonics 2023, 10(10), 1141; https://doi.org/10.3390/photonics10101141 - 11 Oct 2023

Viewed by 956

Abstract

We proposed an active differential intensity (DI) fiber coupled plasmon waveguide resonance (CPWR) sensor based on the mode competition effect in the C-band, aiming to enhance the sensitivity. The sensing head is a fiber probe with a sensing layer of ITO/Au/ITO/TiO₂ film, [...] Read more.

We proposed an active differential intensity (DI) fiber coupled plasmon waveguide resonance (CPWR) sensor based on the mode competition effect in the C-band, aiming to enhance the sensitivity. The sensing head is a fiber probe with a sensing layer of ITO/Au/ITO/TiO₂ film, enabling the excitation of CPWR in the C-band. The narrow CPWR spectrum allows DI interrogation by tracking the intensity of light at two wavelengths. The fiber probe is inserted into a dual-wavelength fiber laser to adjust the intra-cavity loss at the two lasing wavelengths. By using the differential modulation of the reflectivity from the refractive index variations, the mode competition effect is triggered. The powers at two lasing wavelengths change oppositely, enlarging the power difference and then resulting in enhanced sensitivity. The average sensitivity is up to 5702 dB/RIUs, which is 10 times higher than that of conventional DI interrogation. The sensitivity enhancement mechanism based on the mode competition effect provides a new technical approach for enhancing the sensitivity of DI SPR sensors. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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15 pages, 2365 KiB

Open AccessArticle

A Series of Avoided Crossings of Resonances in the System of Several Different Dielectric Resonators Results in Giant Q-Factors

by Konstantin Pichugin, Almas Sadreev and Evgeny Bulgakov

Photonics 2023, 10(9), 973; https://doi.org/10.3390/photonics10090973 - 25 Aug 2023

Cited by 2 | Viewed by 1044

Abstract

On an example of a system of three/four/five/six different coupled coaxial silicon disks, we realize a series of avoided crossings of resonances (ACRs) with respect to the different morphologies for the different scales of each disk. Each next step of ACR accompanied by [...] Read more.

On an example of a system of three/four/five/six different coupled coaxial silicon disks, we realize a series of avoided crossings of resonances (ACRs) with respect to the different morphologies for the different scales of each disk. Each next step of ACR accompanied by the optimization processes of all previous ACRs contributes almost one order of magnitude to the Q-factor. As a result, we achieve unprecedented values for the Q-factors:

6.6

·

10^{4}

for three,

4.8 \cdot 10^{6}

for four,

8.5 \cdot 10^{7}

for five and several billions for six free standing silicon disks. Comparisons to such prominent methods as whispering gallery modes or quasi bound states in the continuum to boost the Q-factor demonstrate the tremendous advantage of the present approach not only in terms of Q-factor values but also in terms of mode volumes. Multipole analysis of the final hybridized resonant mode explains such extremely large Q-factor values. The analysis shows a strong redistribution of radiation owing to the almost-exact destructive interference of the dominating complex multipole radiation amplitudes. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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13 pages, 7431 KiB

Open AccessArticle

AR-HUD Optical System Design and Its Multiple Configurations Analysis

by Qubo Jiang and Zhiyuan Guo

Photonics 2023, 10(9), 954; https://doi.org/10.3390/photonics10090954 - 22 Aug 2023

Cited by 4 | Viewed by 3067

Abstract

The use of augmented reality head-up displays (AR-HUD) in automobile safety driving has drawn more and more interest in recent years. An AR-HUD display system should be developed to fit the vehicle and the complicated traffic environment in order to increase the driver’s [...] Read more.

The use of augmented reality head-up displays (AR-HUD) in automobile safety driving has drawn more and more interest in recent years. An AR-HUD display system should be developed to fit the vehicle and the complicated traffic environment in order to increase the driver’s driving concentration and improve the man–vehicle synchronization. In this article, we suggest an AR-HUD display system with dual-layer virtual-image displays for the near field and far field, as well as further research and design of the adjustment system for multi-depth displays of far-field images. It also examines the EYEBOX horizontal adjustment margin of the dual light path. The analysis results show that the scale of EYEBOX is 120 × 60 mm², the modulation transfer function (MTF) of near-field light path > 0.2 @ 6.7 lp/mm, and the MTF of far-field optical path > 0.4 @ 6.7 lp/mm. The distortion of the near-field optical path is less than 0.86%, and that of the far-field optical path is less than 2.2%. By modifying the folding mirror, the far-field optical path creates an 8 m to 24 m multi-depth virtual picture display. Image quality can be maintained when the near-field and far-field optical paths are moved horizontally by 25 mm and 100 mm, respectively. This study offers guidelines for the multi-depth display, EYEBOX horizontal adjustment, and optical layout of augmented reality head-up displays. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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11 pages, 4176 KiB

Open AccessEditor’s ChoiceArticle

Dual-Band Laser Stealth Based on Quasi Photonic Crystals

by Man Yuan, Jianjing Zhao, Xinye Liao and Xin He

Photonics 2023, 10(8), 931; https://doi.org/10.3390/photonics10080931 - 14 Aug 2023

Cited by 1 | Viewed by 1340

Abstract

A quasi photonic crystal (QPC) dual-band absorber for laser stealth is designed and numerically studied. It consists of a defective two-dimensional photonic crystal on a thick Ni film. The defective photonic crystal is a continuous Ge layer with air holes, but some of [...] Read more.

A quasi photonic crystal (QPC) dual-band absorber for laser stealth is designed and numerically studied. It consists of a defective two-dimensional photonic crystal on a thick Ni film. The defective photonic crystal is a continuous Ge layer with air holes, but some of the holes are periodically removed. Under a normal incidence that is perpendicular to the plane of the defects, the absorptivity can achieve 92.8% at the 1.064 μm wavelength and 93.2% at the 1.55 μm wavelength. Within large incident angles (<45 degrees), the dual-band absorptivity is still >80%. Additionally, the emissivity is as low as 5.8%~20.0% and 2.8%~5.8% in the 3–5 μm and 8–14 μm atmospheric windows. It is found that the introduced defects can couple the incidence into the structure and lead to spectral peaks (electromagnetic resonances) even without the bottom Ni film. With the help of the high-loss Ni film, the resonances are transformed into magnetic or/and electric modes of different orders. As a result, the QPC generates four absorption peaks. They are superimposed in pairs, resulting in enhanced absorption of the two laser wavelengths. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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9 pages, 3563 KiB

Open AccessCommunication

2D Saturable Absorbers for Potential Pulse Generation in the Visible-Wavelength Band

by Jian Peng, Runlin Zhu, Tianci Shen, Yuchun Liu, Yanna Ma and Fuxing Gu

Photonics 2023, 10(5), 543; https://doi.org/10.3390/photonics10050543 - 8 May 2023

Cited by 3 | Viewed by 1758

Abstract

Implementing compact, efficient, and reliable passive pulsed lasers at visible wavelengths is attractive. This paper systematically investigated the thickness-dependent optical absorption characteristics of two-dimensional materials, including graphene, transition-metal dichalcogenides, and dye films at the 532 nm wavelength band, and revealed the effects of [...] Read more.

Implementing compact, efficient, and reliable passive pulsed lasers at visible wavelengths is attractive. This paper systematically investigated the thickness-dependent optical absorption characteristics of two-dimensional materials, including graphene, transition-metal dichalcogenides, and dye films at the 532 nm wavelength band, and revealed the effects of thickness on different optical absorption parameters. The results suggested that dye films are more suitable for loss-sensitive pulsed lasers and graphene is more suitable for modulation depth-sensitive pulsed lasers, while transition-metal dichalcogenide samples have intermediate performance. It can provide guidance for the rational selection of saturable absorbers in pulsed all-fiber lasers to optimize the optical pulse performance in the visible-wavelength band. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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15 pages, 4633 KiB

Open AccessEditor’s ChoiceArticle

Analysis of the Emission Features in CdSe/ZnS Quantum Dot-Doped Polymer Fibers

by Xuefeng Peng, Zhijian Wu, Chen Ye, Yang Ding and Wei Liu

Photonics 2023, 10(3), 327; https://doi.org/10.3390/photonics10030327 - 18 Mar 2023

Cited by 1 | Viewed by 2124

Abstract

The emission features of Cdse/ZnS quantum dots doped step-index polymer optical fibers are computationally analyzed in this paper. Spontaneous emission and amplified spontaneous emission were calculated by a theoretical model based on the rate equations in terms of time, fiber length, and wavelength. [...] Read more.

The emission features of Cdse/ZnS quantum dots doped step-index polymer optical fibers are computationally analyzed in this paper. Spontaneous emission and amplified spontaneous emission were calculated by a theoretical model based on the rate equations in terms of time, fiber length, and wavelength. All the calculated parameters are derived from experiments. Through the comparative analysis of the calculated and experimental results of spontaneous emission, we found that the pump power and overlap between the emission and absorption cross-sections may be the two main reasons for the red shift of the output spectra. When the pump power exceeds the threshold of amplified spontaneous emission, the width of the output spectra will rapidly decrease, the output wavelength will fall back toward the maximum emission cross-section, and the final output wavelength will still be affected by the doping concentration and pump power, while amplified spontaneous emission will not be generated when the total number of doped quantum dots is less than 1.27 × 10¹². Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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13 pages, 3580 KiB

Open AccessArticle

Thermal Lensing and Laser-Induced Damage in Special Pure Chalcogenide Ge₃₅As₁₀S₅₅ and Ge₂₀As₂₂Se₅₈ Glasses under Quasi-CW Fiber Laser Irradiation at 1908 nm

by Oleg Antipov, Anton Dobrynin, Yuri Getmanovskiy, Ella Karaksina, Vladimir Shiryaev, Maksim Sukhanov and Tatiana Kotereva

Photonics 2023, 10(3), 252; https://doi.org/10.3390/photonics10030252 - 28 Feb 2023

Cited by 5 | Viewed by 1952

Abstract

Special pure chalcogenide glass is the material of choice for many mid-infrared optical fibers and fiber lasers. In this paper, the thermo-optical lensing and laser-induced damage were studied in Ge₃₅As₁₀S₅₅ and Ge₂₀As₂₂Se₅₈ glasses [...] Read more.

Special pure chalcogenide glass is the material of choice for many mid-infrared optical fibers and fiber lasers. In this paper, the thermo-optical lensing and laser-induced damage were studied in Ge₃₅As₁₀S₅₅ and Ge₂₀As₂₂Se₅₈ glasses and compared with the well-studied As₂S₃ glass. The thermal Z-scan technique with the quasi-CW Tm-doped fiber laser at 1908 nm was applied to study thermal lensing in chalcogenide glass. The laser-induced damage of various chalcogenide glasses was determined using the one-on-one procedure. The thermal nonlinear refractive index of the Ge₃₅As₁₀S₅₅ and Ge₂₀As₂₂Se₅₈ glasses was found to be lower than that of the As₂S₃ glass. The laser-induced damage threshold of the Ge₂₀As₂₂Se₅₈ glass was determined to be higher than that of the Ge₃₅As₁₀S₅₅ glass. The difference in the thermal damage threshold of the Ge₃₅As₁₀S₅₅ and Ge₂₀As₂₂Se₅₈ glasses and their lower value in comparison with the As₂S₃ glass were explained by a deviation from the stoichiometry of glass compositions and their tendency to crystallize. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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10 pages, 4660 KiB

Open AccessArticle

Polarization-Dependent Absorption and Transmission Metasurfaces for Linearly and Circularly Polarized Light in Terahertz Band

by Bowei Yang, Mingzhao Ouyang, Hang Ren, Jinshuang Wu, Yixin Zhang and Yuegang Fu

Photonics 2023, 10(2), 100; https://doi.org/10.3390/photonics10020100 - 17 Jan 2023

Cited by 2 | Viewed by 2311

Abstract

Polarization detection is an important part of many polarization applications such as polarization imaging, wireless communication, and circular dichroism spectroscopy. In this paper, two polarization-dependent terahertz wave absorption and transmission metasurface for linearly and circularly polarized light are proposed and proved by numerical [...] Read more.

Polarization detection is an important part of many polarization applications such as polarization imaging, wireless communication, and circular dichroism spectroscopy. In this paper, two polarization-dependent terahertz wave absorption and transmission metasurface for linearly and circularly polarized light are proposed and proved by numerical simulations. Polarization filtering and polarization absorption are integrated on a single cell, and the orthogonal polarization component is transmitted and absorbed, respectively. The linearly polarization-dependent transmission and absorption structure can obtain a transmission extinction ratio of 11.5 dB and an absorption extinction ratio of over 270 dB at 3 THz. Moreover, the circularly polarization-dependent structure can obtain a transmission extinction ratio of 8.1 dB and an absorption extinction ratio of 4.66 dB at 2.8 THz. Our design facilitates the acquisition of full Stokes parameters and the high-resolution imaging. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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12 pages, 8933 KiB

Open AccessArticle

Chromatic-Aberration-Corrected Hyperspectral Single-Pixel Imaging

by Ying Liu, Zhao-Hua Yang, Yuan-Jin Yu, Ling-An Wu, Ming-Yue Song and Zhi-Hao Zhao

Photonics 2023, 10(1), 7; https://doi.org/10.3390/photonics10010007 - 22 Dec 2022

Cited by 7 | Viewed by 2957

Abstract

With the emerging development of hyperspectral single-pixel imaging (SPI) systems, the trade-off between the simplicity of optical structure and the correction of chromatic aberration is now an essential factor to be considered. To address both issues simultaneously, we propose a chromatic-aberration-corrected hyperspectral single-pixel [...] Read more.

With the emerging development of hyperspectral single-pixel imaging (SPI) systems, the trade-off between the simplicity of optical structure and the correction of chromatic aberration is now an essential factor to be considered. To address both issues simultaneously, we propose a chromatic-aberration-corrected hyperspectral single-pixel imaging scheme, which is based on spectral measurement and dispersion correction. Its achromatism feature is evaluated by optical simulations and proof-of-concept experiments. Moreover, to overcome the shortcomings of traditional algorithms, a new adaptive iterative algorithm is employed, which can further optimize image quality. The results demonstrate that both dispersion and noise in our system are significantly reduced. Taking the position coordinate variance as a figure of merit, we have realized an order of magnitude improvement in the lateral chromatic aberration over the spectral range of 400–780 nm compared to that in conventional hyperspectral SPI. Meanwhile, the contrast-to-noise ratio in our system is enhanced on average by 3 dB. To the best of our knowledge, this is the first such demonstration, and the technique presents possibilities for future integrated applications of high spatial/spectral resolution over the entire visible range, and the system has the potential to be scaled down for future integrated applications. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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15 pages, 5003 KiB

Open AccessArticle

Optical Design for Aberration Correction of Ultra-Wide Spectral Range Echelle Spectrometer

by Yuming Wang, Youshan Qu, Hui Zhao and Xuewu Fan

Photonics 2022, 9(11), 841; https://doi.org/10.3390/photonics9110841 - 8 Nov 2022

Cited by 4 | Viewed by 1905

Abstract

The echelle grating spectrometer, with a wide spectral range and high-resolution spectral analysis, is one of the best tools for fine spectral measurement. Nevertheless, it suffers from excessive residual aberrations and a large overall size. In this study, the design and implementation of [...] Read more.

The echelle grating spectrometer, with a wide spectral range and high-resolution spectral analysis, is one of the best tools for fine spectral measurement. Nevertheless, it suffers from excessive residual aberrations and a large overall size. In this study, the design and implementation of a novel asymmetric Czerny–Turner ultra-wide spectral range achromatic echelle spectrometer are described. The echelle spectrometer has three channels, and it uses an off-axis parabolic mirror to obtain collimated light without aberrations. Three sets of gratings and dispersive prisms with different coatings are utilized as cross-dispersion elements to acquire two-dimensional images containing spectral information. Suitable detectors are selected according to the requirements of each channel, and three sets of coaxial focusing lenses are designed separately to minimize the aberration. The results of the simulation analysis by ZEMAX indicate that in the entire operating band (200–1100 nm), the root mean square radius of the dispersion spots is ≤ 2.2 μm, all of which are located within the limited range of the size of the detector, thus ensuring that the system’s spectral resolution reaches 0.02 nm at 200 nm, 0.04 nm at 650 nm, and 0.1 nm at 1100 nm. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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15 pages, 2833 KiB

Open AccessArticle

An Optical POCT Device for Colorimetric Detection of Urine Test Strips Based on Raspberry Pi Imaging

by Zixin Yang, Gaozhe Cai, Jianlong Zhao and Shilun Feng

Photonics 2022, 9(10), 784; https://doi.org/10.3390/photonics9100784 - 21 Oct 2022

Cited by 6 | Viewed by 3867

Abstract

Urine examinations are widely applied in hospitals using urine test strip analyzers or other sophisticated professional instruments. However, such methods are inconvenient health monitoring of patients at home. Herein, we construct an optical device for point-of-care testing (POCT) for urine analysis at home [...] Read more.

Urine examinations are widely applied in hospitals using urine test strip analyzers or other sophisticated professional instruments. However, such methods are inconvenient health monitoring of patients at home. Herein, we construct an optical device for point-of-care testing (POCT) for urine analysis at home or on the spot. A black box and color calibration curve are established to eliminate the influence of ambient light with an independent internal lighting system included in the device. A Raspberry Pi with a CSI camera is programmed to automatically collect the strip images and identify the HSV values of the image with an image processing algorithm. During this process, these corrected colors are converted to concentration values by preloaded standard curves. Under optimal conditions, the proposed POCT device can quantitatively and automatically detect glucose within 1 min, with linear detection ranging from 2 mM to 60 mM and a detection limit of 1.16 mM. In addition, the device demonstrates satisfactory accuracy and quantitative analysis of ketone bodies, glucose, protein, occult blood, pH, and leukocytes in human urine samples with high-resolution concentrations, achieving results similar to those obtained with hospital instruments. The proposed device is portable and user-friendly, providing convenient colorimetric analysis for urine. Furthermore, the proposed device also has considerable potential for the development of in vitro diagnosis methods through combination with other test strips. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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9 pages, 1805 KiB

Open AccessCommunication

Sampling Parallel SOA-MZIs Configuration for All-Optical Simultaneous Frequency Down-Conversion

by Hassan Termos and Ali Mansour

Photonics 2022, 9(10), 745; https://doi.org/10.3390/photonics9100745 - 9 Oct 2022

Cited by 5 | Viewed by 1467

Abstract

In this paper, we expound a modulation concept to contrive simultaneous frequency down-conversion based on a three parallel Semiconductor Optical Amplifier Mach-Zehnder Interferometers (SOA-MZIs) link by using a band pass sampling method in a Virtual Photonics Inc. simulator. Each SOA-MZI is deployed to [...] Read more.

In this paper, we expound a modulation concept to contrive simultaneous frequency down-conversion based on a three parallel Semiconductor Optical Amplifier Mach-Zehnder Interferometers (SOA-MZIs) link by using a band pass sampling method in a Virtual Photonics Inc. simulator. Each SOA-MZI is deployed to achieve a down-converted signal, which has ten replicas related to the first ten harmonic ranks of the sampling signal, at the SOA-MZI outer port. Then, the admixture of the three down-converted signals yields a sampled signal, which is called a simultaneous down-converted signal that contains thirty different replicas. The positive down-conversion gains with top values are reached with the sampling parallel SOA-MZIs link. Moreover, we evaluated the quality of the parallel SOA-MZIs transmission system over orthogonal frequency division multiplexing (OFDM) complex modulated signals using the error vector magnitude values as a performance index. The utmost bit rate attained is 2 Gbit/s for OFDM modulations. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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Review

Jump to: Research

21 pages, 4309 KiB

Open AccessReview

The Advances and Applications of Characterization Technique for Exosomes: From Dynamic Light Scattering to Super-Resolution Imaging Technology

by Shijia Wu, Yalan Zhao, Zitong Zhang, Chao Zuo, Hongjun Wu and Yongtao Liu

Photonics 2024, 11(2), 101; https://doi.org/10.3390/photonics11020101 - 23 Jan 2024

Cited by 2 | Viewed by 3040

Abstract

Exosomes distributed by extracellular vesicles carry various information highly consistent with cells, becoming a new type of biomarker for tumor screening. However, although conventional characterization technologies can quantify size and morphology for exosomes, they are limited in related fields such as function tracing, [...] Read more.

Exosomes distributed by extracellular vesicles carry various information highly consistent with cells, becoming a new type of biomarker for tumor screening. However, although conventional characterization technologies can quantify size and morphology for exosomes, they are limited in related fields such as function tracing, protein quantification at unit point, and microstructural information. In this paper, firstly, different exosome characterization methods are systematically reviewed, such as dynamic light scattering, nanoparticle tracking analysis, flow cytometry, electron microscope, and emerging super-resolution imaging technologies. Then, advances in applications are described one by one. Last but not least, we compare the features of different technologies for exosomes and propose that super-resolution imaging technology can not only take into account the advantages of conventional characterization techniques but also provide accurate, real-time, and super-resolution quantitative analysis for exosomes. It provides a fine guide for exosome-related biomedical research, as well as application in liquid biopsy and analysis techniques. Full article

(This article belongs to the Special Issue Advances in Photonic Materials and Technologies)

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