Photonics

20 pages, 8385 KiB

Open AccessArticle

Perfect Nonradiating Modes in Dielectric Nanoparticles

by Vasily Klimov

Photonics 2022, 9(12), 1005; https://doi.org/10.3390/photonics9121005 - 19 Dec 2022

Cited by 4 | Viewed by 1913

A hypothesis of the existence of perfect nonradiating modes in dielectric nanoparticles of an arbitrary shape is put forward. It is strictly mathematically proved that such modes exist in axisymmetric dielectric nanoparticles and have unlimited radiation Q factors. With the smart tuning of [...] Read more.

A hypothesis of the existence of perfect nonradiating modes in dielectric nanoparticles of an arbitrary shape is put forward. It is strictly mathematically proved that such modes exist in axisymmetric dielectric nanoparticles and have unlimited radiation Q factors. With the smart tuning of the excitation beams, perfect modes appear as deep minima in the scattered radiation spectra (up to complete disappearance), but at the same time, they have a substantial amplification of the fields inside the particle. Such modes have no analogs and can be useful for the realization of nanosensors, low threshold nanolasers, and other strong nonlinear effects in nanoparticles. Full article

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8 pages, 3069 KiB

Open AccessCommunication

Convolution Error Reduction for a Fabry–Pérot-Based Linewidth Measurement: A Theoretical and Experimental Study

by Xuanning Hun, Zhenxu Bai, Jianping Wang, Bin Chen, Can Cui, Yulei Wang and Zhiwei Lu

Photonics 2022, 9(12), 1004; https://doi.org/10.3390/photonics9121004 - 19 Dec 2022

Cited by 5 | Viewed by 1632

Abstract

Linewidth measurement of a short pulse single-longitudinal mode laser with a low repetition rate has been a big challenge. Although the Fabry–Pérot (FP) etalon in combination with a beam profiler is an effective approach to measure the linewidth, the convolution error introduced by [...] Read more.

Linewidth measurement of a short pulse single-longitudinal mode laser with a low repetition rate has been a big challenge. Although the Fabry–Pérot (FP) etalon in combination with a beam profiler is an effective approach to measure the linewidth, the convolution error introduced by the inherent transmission spectrum width of an FP restricts the measurement accuracy. Here, the source of convolutional errors of the FP etalon-based linewidth measurement is analyzed, and the convolutional fitting method is proposed to reduce the errors. The results show that the linewidth measurement using the FP cavity with low reflectance (95%) can achieve the same resolution as that with high reflectance (99.5%) based on this convolution error reduction method. The study provides a simple approach to accurately measuring the linewidth of pulsed lasers, even with low energy. Full article

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29 pages, 9649 KiB

Open AccessFeature PaperArticle

AnaBHEL (Analog Black Hole Evaporation via Lasers) Experiment: Concept, Design, and Status

by Pisin Chen, Gerard Mourou, Marc Besancon, Yuji Fukuda, Jean-Francois Glicenstein, Jiwoo Nam, Ching-En Lin, Kuan-Nan Lin, Shu-Xiao Liu, Yung-Kun Liu, Masaki Kando, Kotaro Kondo, Stathes Paganis, Alexander Pirozhkov, Hideaki Takabe, Boris Tuchming, Wei-Po Wang, Naoki Watamura, Jonathan Wheeler and Hsin-Yeh Wu

Photonics 2022, 9(12), 1003; https://doi.org/10.3390/photonics9121003 - 19 Dec 2022

Cited by 11 | Viewed by 3560

Abstract

Accelerating relativistic mirrors have long been recognized as viable settings where the physics mimic those of the black hole Hawking radiation. In 2017, Chen and Mourou proposed a novel method to realize such a system by traversing an ultra-intense laser through a plasma [...] Read more.

Accelerating relativistic mirrors have long been recognized as viable settings where the physics mimic those of the black hole Hawking radiation. In 2017, Chen and Mourou proposed a novel method to realize such a system by traversing an ultra-intense laser through a plasma target with a decreasing density. An international AnaBHEL (Analog Black Hole Evaporation via Lasers) collaboration was formed with the objectives of observing the analog Hawking radiation, shedding light on the information loss paradox. To reach these goals, we plan to first verify the dynamics of the flying plasma mirror and characterize the correspondence between the plasma density gradient and the trajectory of the accelerating plasma mirror. We will then attempt to detect the analog Hawking radiation photons and measure the entanglement between the Hawking photons and their “partner particles”. In this paper, we describe our vision and strategy of AnaBHEL using the Apollon laser as a reference, and we report on the progress of our R&D concerning the key components in this experiment, including the supersonic gas jet with a graded density profile, and the superconducting nanowire single-photon Hawking detector. In parallel to these hardware efforts, we performed computer simulations to estimate the potential backgrounds, and derived analytic expressions for modifications to the blackbody spectrum of the Hawking radiation for a perfectly reflecting point mirror, due to the semi-transparency and finite-size effects specific to flying plasma mirrors. Based on this more realistic radiation spectrum, we estimate the Hawking photon yield to guide the design of the AnaBHEL experiment, which appears to be achievable. Full article

(This article belongs to the Special Issue Progress in Laser Accelerator and Future Prospects)

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11 pages, 2814 KiB

Open AccessCommunication

Theoretical Analysis of Continuous-Wave Mid-Infrared Optical Vortex Source Generated by Singly Resonant Optical Parametric Oscillator

by Ziheng Zhou, Shirui Zhang, Yuanhao Duan, Minghao Guo and Peng Li

Photonics 2022, 9(12), 1002; https://doi.org/10.3390/photonics9121002 - 19 Dec 2022

Cited by 1 | Viewed by 1769

Abstract

Due to the important application in the study of vibrational circular dichroism and helical dichroism of chiral molecules, the tunable vortex beam at mid-infrared region has attracted increasing attention. Based on orbital angular momentum (OAM) conservation in nonlinear interactions, the vortex pumped singly [...] Read more.

Due to the important application in the study of vibrational circular dichroism and helical dichroism of chiral molecules, the tunable vortex beam at mid-infrared region has attracted increasing attention. Based on orbital angular momentum (OAM) conservation in nonlinear interactions, the vortex pumped singly resonant optical parametric oscillator (SRO) is recognized as a versatile source of coherent vortex radiation providing high power and broad wavelength coverage from a single device. However, the low parametric gain and high oscillation threshold under continuous wave (cw) pumping has so far been the most challenging factor in generating cw tunable vortex beams. To predict the output characteristic of vortex pumped SRO, a theoretical model describing the vortex pumped SRO is needed. In this study, the theoretical model describing the vortex pumped SRO is set up under collimated Gaussian beam approximation. Output characteristics of different SROs are simulated numerically. By proper selection of pump scheme (such as double-pass pumping scheme), the vortex pumped mid-infrared SRO can oscillate at a relatively low pump power. By controlling the gain (mode overlap ratio between the pump and resonant wave in the nonlinear crystal) and loss (employing a spot-defect mirror with different defect size as the output coupler) of the resonant signal mode in the SRO, the OAM of the pump beam can be directionally transferred to a specific down converted beam. The transfer mechanism of the OAM among the pump light and the down-converted beams and factors affecting the transfer are studied. Our study provides the guidelines for the design and optimization of vortex pumped SRO under cw operation. Full article

(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)

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13 pages, 6891 KiB

Open AccessArticle

Carbon Monoxide Detection Based on the Carbon Nanotube-Coated Fiber Gas Sensor

by Yin Zhang, Wenwen Yu, Dibo Wang, Ran Zhuo, Mingli Fu and Xiaoxing Zhang

Photonics 2022, 9(12), 1001; https://doi.org/10.3390/photonics9121001 - 19 Dec 2022

Cited by 4 | Viewed by 2410

Abstract

Accurate detection of the internal decomposition components of SF₆ electrical equipment plays an important role in the evaluation of equipment status. However, gas samples are usually taken out for detection at present, which makes it difficult to understand the real situation inside [...] Read more.

Accurate detection of the internal decomposition components of SF₆ electrical equipment plays an important role in the evaluation of equipment status. However, gas samples are usually taken out for detection at present, which makes it difficult to understand the real situation inside the equipment. In this paper, a carbon nanotube-coated fiber gas sensor is proposed, which has the potential to be applied as a built-in gas sensor. The fiber loop ring-down (FLRD) gas detection system based on the carbon nanotube-coated fiber gas sensor was built, and the detectable decomposition components among the four typical SF₆ decomposition components of SO₂, SO₂F₂ and SOF₂ and CO were analyzed. The results showed that the fiber gas sensor was most sensitive to CO. Based on density functional theory, it was found that single-walled carbon nanotubes had the best adsorption effect on CO molecules under the same conditions, with the adsorption energy reaching −0.150 Ha. The detection performance of the system for CO was studied, and the results showed that there was a good linear relationship between CO concentration and ring-down time: R² was 0.984, the maximum inversion error of 0~200 ppm CO was 1.916 ppm, and the relative error was 4.10%. The sensitivity of the system was 0.183 ns/ppm, and the detection limit of the system was 19.951 ppm. The system had good stability, with the standard deviation of single-point repeatability being 0.00356, and the standard deviation of the long period of the experiment being 0.00606. The research results provide a new idea for the detection of SF₆ decomposition components, and lay the foundation for the component detection method of built-in fiber sensor of SF₆ electrical equipment. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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6 pages, 1020 KiB

Open AccessCommunication

Spectral Broadening of Chirped Laser Pulse Caused by Four-Wave Mixing in BaWO₄ Crystals

by Igor Kinyaevskiy, Leonid Seleznev and Andrey Ionin

Photonics 2022, 9(12), 1000; https://doi.org/10.3390/photonics9121000 - 19 Dec 2022

Cited by 2 | Viewed by 1761

Abstract

The spectral broadening of a chirped, temporally stretched (up to 200 ps) Ti:sapphire laser pulse propagating together with a broadband low-power seed pulse through BaWO₄ crystals was experimentally and numerically studied. Our analysis demonstrated that self-phase modulation could not have affected the [...] Read more.

The spectral broadening of a chirped, temporally stretched (up to 200 ps) Ti:sapphire laser pulse propagating together with a broadband low-power seed pulse through BaWO₄ crystals was experimentally and numerically studied. Our analysis demonstrated that self-phase modulation could not have affected the pulse spectrum under the experimental conditions. The spectral broadening of the Ti:sapphire laser pulse was found to be due to four-wave mixing, which resulted in transferring the power of the central wavelength to the spectral wings. To the best of our knowledge, this is the first demonstration of such origin of laser pulse spectral broadening in crystals. Full article

(This article belongs to the Section Optical Interaction Science)

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9 pages, 1249 KiB

Open AccessArticle

Principle and Performance Analysis of the Levenberg–Marquardt Algorithm in WMS Spectral Line Fitting

by Yongjie Sun, Pengpeng Wang, Tingting Zhang, Kun Li, Feng Peng and Cunguang Zhu

Photonics 2022, 9(12), 999; https://doi.org/10.3390/photonics9120999 - 18 Dec 2022

Cited by 6 | Viewed by 2116

Abstract

Calibration-free wavelength modulation spectroscopy (WMS) is an efficient technique for trace gas monitoring. It is widely used due to its resistance to light intensity fluctuations, strong suppression of low-frequency noise, fast response time, and excellent environmental adaptability. The calibration-free WMS often employs the [...] Read more.

Calibration-free wavelength modulation spectroscopy (WMS) is an efficient technique for trace gas monitoring. It is widely used due to its resistance to light intensity fluctuations, strong suppression of low-frequency noise, fast response time, and excellent environmental adaptability. The calibration-free WMS often employs the Levenberg–Marquardt algorithm for spectral fitting to retrieve gas characteristics. However, to the best of our knowledge, an analysis of the main factors affecting the operational effectiveness of the Levenberg–Marquardt algorithm in calibration-free WMS has merely been reported. In this paper, we have systematically analyzed the Levenberg–Marquardt algorithm’s operating mechanism in WMS-2f/1f. The results show that the number of parameters and the estimation errors of the initial parameters are the main factors limiting the retrieval accuracy of the algorithm, which provides some important guidelines for the subsequent optimization of the spectral fitting scheme. Full article

(This article belongs to the Special Issue Applications of Laser Spectroscopy)

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14 pages, 14620 KiB

Open AccessArticle

Manipulation of Energy Flow with X-Type Vortex

by Han Zhang, Tianhu Zhang, Xinying Zhao and Xiaoyan Pang

Photonics 2022, 9(12), 998; https://doi.org/10.3390/photonics9120998 - 17 Dec 2022

Viewed by 1509

Abstract

In this study, a new method for manipulating energy flow in a 3D vector field is proposed. In this method, an azimuthally-polarized beam with a noncanonical vortex, the X-type vortex, is focused in a high-numerical aperture system. It is found that, instead of [...] Read more.

In this study, a new method for manipulating energy flow in a 3D vector field is proposed. In this method, an azimuthally-polarized beam with a noncanonical vortex, the X-type vortex, is focused in a high-numerical aperture system. It is found that, instead of the invariance of the energy flow which is characteristic of the traditional vortex (i.e., canonical vortex), both the longitudinal and the transverse energy flows in virtue of the X-type vortex rotate around the beam center as the beam propagates, and this rotational behavior (including the maxima location and the rotational angle) can be adjusted by the anisotropic parameter and the order the X-type vortex. Through defining a complex transverse Poynting field and applying the equivalence principle, the transverse energy flow and its topological reactions are discussed in the focal plane. Our result shows that, by changing the anisotropic parameter of the X-type vortex, rich topological reactions will occur, resulting in various distribution patterns of the energy flow, such as multi vortex-type singularities around the beam center. Our research demonstrates newly-observed features of the X-type vortex and also provides a simple method to manipulate energy flows both along longitudinal and transverse directions, which will be useful in optical manipulations. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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11 pages, 3086 KiB

Open AccessCommunication

Visible to Mid-Infrared Supercontinuum Initiated by Stimulated Raman Scattering of 1.03 μm Ultrashort Pulses in a Gas-Filled Silica Fiber

by Alexey Gladyshev, Yury Yatsenko, Anton Kolyadin and Igor Bufetov

Photonics 2022, 9(12), 997; https://doi.org/10.3390/photonics9120997 - 17 Dec 2022

Cited by 13 | Viewed by 1584

Abstract

Multiband supercontinuum generation covering the bandwidth from 0.65 μm to 3.3 μm was demonstrated in a gas-filled hollow-core silica fiber pumped by chirped ultrashort pulses at 1.03 μm. The development of the SC spectrum into the mid-IR was initiated by cascade stimulated Raman [...] Read more.

Multiband supercontinuum generation covering the bandwidth from 0.65 μm to 3.3 μm was demonstrated in a gas-filled hollow-core silica fiber pumped by chirped ultrashort pulses at 1.03 μm. The development of the SC spectrum into the mid-IR was initiated by cascade stimulated Raman scattering in gaseous D₂, which was used as an active medium filling the hollow core. The influence of the Kerr nonlinearity was studied by changing the linear chirp of the pump pulses. The influence of gas pressure and pump pulse energy on the SC generation was investigated. As high as 14% of pump quanta were converted to the wavelength range above 2 μm. Full article

(This article belongs to the Special Issue Light Control and Particle Manipulation)

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13 pages, 3085 KiB

Open AccessArticle

Photoelectron Yield Spectroscopy and Transient Photocurrent Analysis for Triphenylamine-Based Photorefractive Polymer Composites

by Naoto Tsutsumi, Yusuke Mizuno, Boaz Jessie Jackin, Kenji Kinashi, Takafumi Sassa, Ha Ngoc Giang and Wataru Sakai

Photonics 2022, 9(12), 996; https://doi.org/10.3390/photonics9120996 - 17 Dec 2022

Cited by 1 | Viewed by 1821

Abstract

The photocurrent for poly(4-(dimethylamino)benzyl acrylate) (PDAA) photorefractive composites with (4-(diphenylamino)phenyl)methanol (TPAOH) photoconductive plasticizers was measured to be two orders of magnitude higher than that obtained with (2,4,6-trimethylphenyl)diphenylamine (TAA) photoconductive plasticizers. In this study, to determine the reason for the large difference in the [...] Read more.

The photocurrent for poly(4-(dimethylamino)benzyl acrylate) (PDAA) photorefractive composites with (4-(diphenylamino)phenyl)methanol (TPAOH) photoconductive plasticizers was measured to be two orders of magnitude higher than that obtained with (2,4,6-trimethylphenyl)diphenylamine (TAA) photoconductive plasticizers. In this study, to determine the reason for the large difference in the photocurrent measured for PDAA photorefractive composites containing two different photoconductive plasticizers of TPAOH and TAA, the highest occupied molecular orbital (HOMO) level identical to the ionization potential (I_p) and the width of the density of states (DOS) were evaluated using photoelectron yield spectroscopy, and the transient photocurrent was analyzed using a two-trap model. The estimated hole mobility was also rationalized using a Bässler formalism together with the energetic disorder of the width of the DOS and the positional disorder of the scattering situation for carrier hopping. Full article

(This article belongs to the Special Issue Photorefractive Photonics and Beyond)

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16 pages, 6897 KiB

Open AccessArticle

Relaxation of Beam Irradiation Accuracy of Cooperative Optical Wireless Power Transmission in Terms of Fly Eye Module with Beam Confinement Mechanism

by Kaoru Asaba and Tomoyuki Miyamoto

Photonics 2022, 9(12), 995; https://doi.org/10.3390/photonics9120995 - 16 Dec 2022

Cited by 7 | Viewed by 1681

Abstract

In optical wireless power transmission (OWPT) systems, since beam size is finite, and relative position and attitude between transmitter and receiver is not always stationary, both beam alignment and shaping accuracies are important parameters. Analysis based on a power generation efficiency calculation model [...] Read more.

In optical wireless power transmission (OWPT) systems, since beam size is finite, and relative position and attitude between transmitter and receiver is not always stationary, both beam alignment and shaping accuracies are important parameters. Analysis based on a power generation efficiency calculation model of general OWPT systems shows that their tolerances are quite demanding, especially for long range OWPT, and relaxation is inescapably necessary. This study introduces the fly eye lens as a candidate to relax these difficulties and, moreover, it features producing homogeneous irradiation onto the solar cell array. All of these are essential to OWPT systems. In this study, cooperative OWPT is discussed, in which solar cell array and power transmitter mutually align each other. Its efficiency calculation model is integrated with a fly eye module surrounded by reflective walls. System level requirements are analyzed regarding beam shaping and alignment in terms of power generation ratio, and it is clarified that this module largely relaxes requirements. In this module, beam power is confined within the module and will be eventually absorbed by the solar cell as the incident beam is within the acceptance angle. This feature avoids degradation of power generation ratio due to beam shape mismatch. These advantages bring progress towards building operational OWPT. Full article

(This article belongs to the Special Issue Latest Papers Related to OWPT 2019-22 on the Topics of Photovoltaic Components, Devices and Systems)

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16 pages, 4668 KiB

Open AccessArticle

Photoinduced Electron Transfer and Aggregation-Induced Emission in 1,8-Naphthalimide Probes as a Platform for Detection of Acid/Base Vapors

by Nikolai I. Georgiev, Ventsislav V. Bakov and Vladimir B. Bojinov

Photonics 2022, 9(12), 994; https://doi.org/10.3390/photonics9120994 - 16 Dec 2022

Cited by 8 | Viewed by 2029

Abstract

In the last few decades, photoinduced electron transfer (PET) based on “fluorophore-spacer-receptor” format became the most popular approach in the design of fluorescent sensing probes. As a result, a variety of architectures for detection of different chemical species has been synthesized, and PET [...] Read more.

In the last few decades, photoinduced electron transfer (PET) based on “fluorophore-spacer-receptor” format became the most popular approach in the design of fluorescent sensing probes. As a result, a variety of architectures for detection of different chemical species has been synthesized, and PET has been well-studied in liquid solutions. The extension of the principles of molecular sensors from liquid solution onto solid support is currently a major task, which opens up new directions for practical applications. An approach for the design of solid state fluorescence-sensing materials could be based on aggregation-induced emission (AIE). That is why, herein, we focused our attention on the investigation of some 1,8-naphthalimides designed on classical “fluorophore-spacer-receptor” to serve as fluorescence-sensing materials in solid state via simultaneous PET and AIE. The effects of different substituents were investigated, and it was found that the examined compounds with well-pronounced AIE could be used as an efficient platform for rapid detection of pH and acid/base vapors in solid state. Full article

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12 pages, 1884 KiB

Open AccessArticle

In Vivo and In Silico Study of Photodynamic Necrosis Volume in Rat Liver

by Marlon Rodrigues Garcia, Víctor Sánchez, Thereza Cury Fortunato, Michelle Barreto Requena, Clóvis Grecco, José Dirceu Vollet-Filho, Layla Pires, Lilian Tan Moriyama and Sebastião Pratavieira

Photonics 2022, 9(12), 993; https://doi.org/10.3390/photonics9120993 - 16 Dec 2022

Cited by 1 | Viewed by 1435

Abstract

Photodynamic therapy is a treatment modality that can be used to treat various types of lesions. To produce cell death, reaching a certain threshold dose of reactive oxygen species (ROS) is required. The estimation of ROS production is of paramount importance to predict [...] Read more.

Photodynamic therapy is a treatment modality that can be used to treat various types of lesions. To produce cell death, reaching a certain threshold dose of reactive oxygen species (ROS) is required. The estimation of ROS production is of paramount importance to predict the depth of necrosis and to ensure that the volume to be treated receives doses higher than the threshold. In this study, we compared a theoretical model for PDT based on Monte Carlo simulations of light irradiance and rate equations with a rat liver model. At the end of the simulation, necrosis depths and volumes were estimated, as well as the photosensitizer (PS), oxygen, and ROS concentrations at each position of the treated area. From the in vivo study, we obtained the ROS concentration threshold of about 1 mM for Photogem in rat liver. This proposed method can be used for any PS or tissue, including tissues with multiple layers. The proposed method can be used to estimate parameters for any PS or tissue, including layered tissues, as long as their parameters are known. In addition, other protocols can be tested, or compared with the standard ones, providing the bases for analyzing a diverse range of photodynamic treatment scenarios. Full article

(This article belongs to the Special Issue Light-Based Technologies and Spectroscopic Techniques for Photo-Sensing and Photoinactivation of Microorganisms, Virus, and Cancer Cells)

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15 pages, 2815 KiB

Open AccessArticle

An Effective Method for Gas-Leak Area Detection and Gas Identification with Mid-Infrared Image

by Qi Zhao, Xiaoxi Nie, Dong Luo, Jue Wang, Qiran Li and Wei Chen

Photonics 2022, 9(12), 992; https://doi.org/10.3390/photonics9120992 - 16 Dec 2022

Cited by 11 | Viewed by 3852

Abstract

Mid-infrared imaging systems are widely applied in gas-leak detection. However, infrared images generally suffer from low contrast and poor quality. In this paper, an image-enhancement method based on Gaussian filtering and adaptive histogram segmentation is proposed to effectively improve the quality of infrared [...] Read more.

Mid-infrared imaging systems are widely applied in gas-leak detection. However, infrared images generally suffer from low contrast and poor quality. In this paper, an image-enhancement method based on Gaussian filtering and adaptive histogram segmentation is proposed to effectively improve the quality of infrared images. It can effectively improve the quality of infrared images, which contributes to the subsequent gas-image feature extraction. The traditional background modeling algorithm is analyzed, and the ViBe (visual background extractor) algorithm is studied in depth. Based on the advantages and disadvantages of the ViBe algorithm and the characteristics of gas-leak images, a gas-leak region detection method based on the improved ViBe algorithm is proposed. The test results show that it can quickly establish a background model, segment the gas-leak region with motion characteristics, and render the gas-leak region in color based on grayscale mapping to achieve the automatic detection and enhanced display of gas leaks. Full article

(This article belongs to the Special Issue Mid-Infrared Integrated Photonics)

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13 pages, 2566 KiB

Open AccessArticle

Unveiling the Role of the Beam Shape in Photothermal Beam Deflection Measurements: A 1D and 2D Complex Geometrical Optics Model Approach

by Mohanachandran Nair Sindhu Swapna, Dorota Korte and Sankaranarayana Iyer Sankararaman

Photonics 2022, 9(12), 991; https://doi.org/10.3390/photonics9120991 - 16 Dec 2022

Cited by 3 | Viewed by 1693

Abstract

The preponderance of laser beam shapes cannot be ruled out during the implementation of an optical experiment nor during the formulation of its theoretical background. The present work elucidates the role of Gaussian and top-hat beam shapes in generating and analysing the photothermal [...] Read more.

The preponderance of laser beam shapes cannot be ruled out during the implementation of an optical experiment nor during the formulation of its theoretical background. The present work elucidates the role of Gaussian and top-hat beam shapes in generating and analysing the photothermal beam deflection (PBD) signals. The complex geometrical optics models encompassing the perturbations in the phase and amplitude of the probe beam with one-dimensional (1D) and two-dimensional (2D) approaches is employed to curve fit the PBD signal and are compared. From the fitted curve, the thermal diffusivity and conductivity of the sample are calculated with the 1D and 2D models. A uniform intensity distribution over the sample, like a top-hat beam, is achieved using an optical lens system and verified using a beam profiler. When the phase and amplitude of the PBD signal are fitted at different positions of the lens, i.e., in focussed and defocussed conditions, it is observed that difference in the measured thermal characteristics is about 30% for the Gaussian pump beam profile, whereas it is only <4% for top-hat beam. Even though the fitting accuracy and sum of residues estimated for the 2D model are better than 1D, the ease of computation with the 1D model employing top-hat excitation suggests the application of the top-hat profile in photothermal experiments. Full article

(This article belongs to the Special Issue Adaptive Optics and Its Applications)

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13 pages, 4087 KiB

Open AccessArticle

Lighting-Induced Changes in Central and Peripheral Retinal Thickness and Shape after Short-Term Reading Tasks in Electronic Devices

by Elvira Orduna-Hospital, Francisco J. Ávila, Guisela Fernández-Espinosa and Ana Sanchez-Cano

Photonics 2022, 9(12), 990; https://doi.org/10.3390/photonics9120990 - 16 Dec 2022

Cited by 4 | Viewed by 2556

Abstract

Background: To assess retinal and optical changes associated with near vision reading for different lighting conditions in electronic screens. Methods: Twenty-four young healthy subjects participated in the study; an iPad and an Ebook were chosen as stimuli for 5 min of reading task [...] Read more.

Background: To assess retinal and optical changes associated with near vision reading for different lighting conditions in electronic screens. Methods: Twenty-four young healthy subjects participated in the study; an iPad and an Ebook were chosen as stimuli for 5 min of reading task with different lighting conditions. Central and peripheral retinal thicknesses in the macular ETDRS areas by optical coherence tomography were analyzed. Results: Significant differences were found between basal retinal thickness and retinal thickness after reading with iPad and high illumination, in the N6 (p = 0.021) and I6 (p = 0.049) areas, and low illumination (S3: p = 0.008, N3: p = 0.018, I3: p = 0.021, N6: p = 0.018 and I6: p = 0.020), being thinner after reading. The same trend was observed after reading with an Ebook and high lighting in the N3 (p = 0.037) and N6 (p = 0.028). For low lighting conditions, only retinal thinning was observed. After reading, retinal shape analysis revealed significant changes from computed basal eccentricity for high lighting conditions only. At the periphery, those differences in eccentricity values were statistically significant for both lighting conditions. Conclusions: Young people can recover visual quality after 5 min of reading tasks at different lighting levels on electronic devices, while peripheral retinal expansion remains altered, especially at low lighting levels. Full article

(This article belongs to the Special Issue Optics of the Eye: From Visual Optics to Clinical Application)

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7 pages, 1483 KiB

Open AccessCommunication

Transversal Kerr Effect Enhancement of Permalloy-Based Shallow Lamellar Magnetoplasmonic Crystals

by Dmitry Murzin, Victor Belyaev, Johannes Kern, Corinna Kaspar, Wolfram H. Pernice, Rudolf Bratschitsch and Valeria Rodionova

Photonics 2022, 9(12), 989; https://doi.org/10.3390/photonics9120989 - 16 Dec 2022

Viewed by 1692

Abstract

This work demonstrates spectral dependencies of reflectivity and the transversal Kerr effect of a series of permalloy magnetoplasmonic crystals based on shallow lamellar diffraction gratings with a period of 500 nm, stripe’s width of 250 nm, and diffraction stripes’ heights of 28, 43, [...] Read more.

This work demonstrates spectral dependencies of reflectivity and the transversal Kerr effect of a series of permalloy magnetoplasmonic crystals based on shallow lamellar diffraction gratings with a period of 500 nm, stripe’s width of 250 nm, and diffraction stripes’ heights of 28, 43, 67, and 88 nm. The fabricated magnetoplasmonic crystals show a monotonic increase of the transversal Kerr effect and the diffraction figure-of-merit with higher diffraction stripes. The maximum achieved modulation value of the transversal Kerr effect was found to be 0.78%, which can be further tuned by the periodicity and stripes width of the magnetoplasmonic crystals. Full article

(This article belongs to the Special Issue Recent Advances in Optical Diffraction and Imaging)

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15 pages, 3084 KiB

Open AccessArticle

Design and Optimization of Asymmetric Grating Assisted Slot Microring

by Chunjuan Liu, Jiawei Wang, Xiaosuo Wu, Xiaoli Sun, Ze Qiao, Yuqiang Xin and Jiangfeng Zhang

Photonics 2022, 9(12), 988; https://doi.org/10.3390/photonics9120988 - 15 Dec 2022

Cited by 1 | Viewed by 2632

Abstract

In this paper, a slot microring with an asymmetric grating structure is proposed. Through the coupling between the grating and the slot microring, a high free spectral range or EIT-like effects with a high quality factor can be achieved in the same device. [...] Read more.

In this paper, a slot microring with an asymmetric grating structure is proposed. Through the coupling between the grating and the slot microring, a high free spectral range or EIT-like effects with a high quality factor can be achieved in the same device. The grating is designed as an asymmetric structure to realize the modulation of the optical signal and the control of the resonance peak by changing the grid number, and the effect of different grating periods on the output spectrum is explored. The results show that changing the grating on slot sidewalls can increase or decrease the number of resonant peaks. By selecting a specific period of the gratings on both sides of the slot, the distance between adjacent resonance peaks can be increased to achieve modulation of the free spectral range. In this paper, depending on the grating period, we obtain a quality factor of 5016 and an FSR of 137 nm, or a quality factor of 10,730 and an FSR of 92 nm. The refractive index sensing simulation is carried out for one of the periods, which can achieve a sensitivity of 370 nm/RIU. Therefore, the proposed new structure has certain advantages in different sensing applications. Full article

(This article belongs to the Special Issue Integrated Waveguide-Based Photonic Devices)

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33 pages, 7105 KiB

Open AccessReview

Optical Fiber Biosensors for Protein Detection: A Review

by Shuhan Lyu, Zheyu Wu, Xinghua Shi and Qian Wu

Photonics 2022, 9(12), 987; https://doi.org/10.3390/photonics9120987 - 15 Dec 2022

Cited by 9 | Viewed by 4328

Abstract

Proteins play an important role in organisms. The fast and high-accuracy detection of proteins is demanded in various fields, such as healthcare, food safty, and biosecurity, especially in the background of the globally raging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Optical fiber [...] Read more.

Proteins play an important role in organisms. The fast and high-accuracy detection of proteins is demanded in various fields, such as healthcare, food safty, and biosecurity, especially in the background of the globally raging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Optical fiber sensors have great potential for protein detection due to the excellent characteristics of high sensitivity, miniaturization, and capability for remote monitoring. Over the past decades, a large number of structures have been investigated and proposed. This paper begins with an overview of different fiber sensing structures for protein detection according to the fundamental sensing mechanisms. The overview is classified into four sections, including intensity-modulation, phase-modulation, scattering, and fluorescence. In each section, we reviewed the recent advances of fiber protein sensors and compared their performance, such as sensitivity and limit of detection. And then we analyzed the advantages and disadvantages of the four kinds of biosensors. Finally, the paper concludes with the challenges faced and possible future development of optical fiber protein biosensors for further study. Full article

(This article belongs to the Special Issue Advances of Optical Fiber Sensors)

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12 pages, 2941 KiB

Open AccessArticle

Non-Mechanical Multiplexed Beam-Steering Elements Based on Double-Sided Liquid Crystal Metasurfaces

by Maxim V. Gorkunov, Artur R. Geivandov, Alena V. Mamonova, Ivan V. Simdyankin, Irina V. Kasyanova, Alexander A. Ezhov and Vladimir V. Artemov

Photonics 2022, 9(12), 986; https://doi.org/10.3390/photonics9120986 - 15 Dec 2022

Cited by 1 | Viewed by 2041

Abstract

We propose, optimize, fabricate and test beam-steering elements based on double-sided liquid-crystal (LC) metasurfaces allowing for diffractive and spectral multiplexing, and thus covering three different beam deflection directions each. While straightforward parallel design requires one diffractive beam-steering element per a direction determined by [...] Read more.

We propose, optimize, fabricate and test beam-steering elements based on double-sided liquid-crystal (LC) metasurfaces allowing for diffractive and spectral multiplexing, and thus covering three different beam deflection directions each. While straightforward parallel design requires one diffractive beam-steering element per a direction determined by Bragg’s law, double-sided LC-metasurfaces are remarkably flexible and allow optimization for three operation modes at different applied voltages: zero-voltage mode with dominant +1 order red light and +2 order blue light diffraction; intermediate mode at 1.4–1.6 V voltage with dominant +1 order blue light diffraction; and transparent mode at 5 V voltage. We comprehensively study three such elements with 6, 8 and 10 micrometer periods and verify their capability of deflecting blue and red light beams with 40–70% efficiencies in nine target directions with 10 ms characteristic switching times. Full article

(This article belongs to the Special Issue Active/Reconfigurable Metasurfaces)

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8 pages, 815 KiB

Open AccessCommunication

Influence of Gold Nanoantennas on the Photoluminescence of Silicon Nanocrystals

by Ronja Köthemann, Christian Golla, Hong Qu and Cedrik Meier

Photonics 2022, 9(12), 985; https://doi.org/10.3390/photonics9120985 - 15 Dec 2022

Cited by 1 | Viewed by 1312

Abstract

We study the influence of gold nanoantennas on the photoluminescence signal of silicon nanocrystals. Unlike bulk silicon, which only exhibits low photoluminescence at room temperature due to its indirect band gap, silicon nanocrystals have the advantage of producing strong and size-dependent photoluminescence. Here, [...] Read more.

We study the influence of gold nanoantennas on the photoluminescence signal of silicon nanocrystals. Unlike bulk silicon, which only exhibits low photoluminescence at room temperature due to its indirect band gap, silicon nanocrystals have the advantage of producing strong and size-dependent photoluminescence. Here, we place gold nanoantennas on a layered system in which silicon nanocrystals are integrated. The nanoantennas are embedded in the layered system by subsequent overgrowth. We find that the photoluminescence signal can be manipulated ranging from attenuation to enhancement. Moreover, we investigate the impact of grating coupling and the number of antennas per antenna array on the amplification of the photoluminescence signal. Full article

(This article belongs to the Section Optoelectronics and Optical Materials)

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11 pages, 2222 KiB

Open AccessArticle

Performance of SALP Swarm Localization Algorithm in Underwater Wireless Sensor Networks

by Yogeshwary Bommenahalli Huchegowda, Aravind Bettadahalli Ningappa, Naveen Kumar Chandramma Mallesh and Yashwanth Nanjappa

Photonics 2022, 9(12), 984; https://doi.org/10.3390/photonics9120984 - 14 Dec 2022

Cited by 5 | Viewed by 1573

Abstract

In underwater wireless sensor networks, the optimization strategies for localization might be seen as a new boon for the localization of sensor nodes (UWSNs). The techniques for optimization are those that repair the incorrect value, adapt it to the situation, and correct it. [...] Read more.

In underwater wireless sensor networks, the optimization strategies for localization might be seen as a new boon for the localization of sensor nodes (UWSNs). The techniques for optimization are those that repair the incorrect value, adapt it to the situation, and correct it. Because the algorithm could adapt to the constantly changing environment, it was widely used in terrestrial applications, and the same can be extended to the underwater environment with modifications. To address the localization issue that arises in UWSNs, the Underwater Salp Swarm Algorithm (USSA), a nature-inspired node localization algorithm, has been presented. With the help of this technique, an effort to discover a solution to the localization problem as an optimization problem is considered. The proposed algorithm is accessed in a simulated water environment. The energy is assigned to the anchor well as non-localized nodes, after deploying them in the simulated underwater network. The suggested algorithm is compared with other optimization algorithms, such as UPSO and UBOA, with reference to the computing time, localization accuracy, and the number of localized nodes. It is possible to localize a greater number of nodes in a much faster and more efficient way by considering the proposed algorithm. Full article

(This article belongs to the Special Issue Optical Wireless Communication for Underwater-to-Ground-to-Space Connectivity)

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14 pages, 11696 KiB

Open AccessArticle

A Semi-Supervised Method for PatchMatch Multi-View Stereo with Sparse Points

by Weida Zhan, Keliang Cao, Yichun Jiang, Yu Chen, Jiale Wang and Yang Hong

Photonics 2022, 9(12), 983; https://doi.org/10.3390/photonics9120983 - 14 Dec 2022

Cited by 2 | Viewed by 2012

Abstract

Recently, the deep-learning-based PatchMatch method has been rapidly developed in 3D reconstruction, based on which boundary regions are filled with other parts that most closely match edge parts, but limited PatchMatch data hinder the generalization of the method to unknown settings. If various [...] Read more.

Recently, the deep-learning-based PatchMatch method has been rapidly developed in 3D reconstruction, based on which boundary regions are filled with other parts that most closely match edge parts, but limited PatchMatch data hinder the generalization of the method to unknown settings. If various large-scale PatchMatch datasets are generated, the process would require considerable time and resources when performing neighborhood point-matching calculations using random iterative algorithms. To solve this issue, we first propose a new, sparse, semi-supervised stereo-matching framework called SGT-PatchMatchNet, which can reconstruct reliable 3D structures with a small number of 3D points using the ground truth of surface frame values. Secondly, in order to solve the problem of the luminosity inconsistency of some pixels in other views, a photometric similar-point loss function is proposed to improve the performance of 3D reconstruction, which causes the neighborhood information to project the depth value of the predicted depth to meet the same 3D coordinates. Finally, in order to solve the problem of the edge blurring of the depth map obtained using the network model, we propose a robust-point consistency loss function to improve the integrity and robustness of the occlusion and edge areas. The experimental results show that the proposed method not only has good visual effects and performance indicators but can also effectively reduce the amount of computation and improve the calculation time. Full article

(This article belongs to the Section New Applications Enabled by Photonics Technologies and Systems)

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9 pages, 2722 KiB

Open AccessArticle

Nanoscale Refractive Index Sensors Based on Fano Resonance Phenomena

by Yifeng Ren, Qiang Wang, Lifang Shen, Feng Liu, Yang Cui, Chuanhui Zhu, Zhanbo Chen, Biyi Huang and Shubin Yan

Photonics 2022, 9(12), 982; https://doi.org/10.3390/photonics9120982 - 14 Dec 2022

Cited by 3 | Viewed by 3450

Abstract

In this paper, a new refractive index sensor based on Fano resonance is introduced. It is mainly composed of two parts: a metal–insulator–metal as a base waveguide and an annular resonant cavity with a double notch and a double convex circle as a [...] Read more.

In this paper, a new refractive index sensor based on Fano resonance is introduced. It is mainly composed of two parts: a metal–insulator–metal as a base waveguide and an annular resonant cavity with a double notch and a double convex circle as a coupling structure. The sensing characteristics of the design are investigated via finite element calculations. The influence of the remaining structure parameters on the system’s sensing performance and the relationship between the wavelength corresponding to the Fano trough and the refractive index are also investigated. Furthermore, the structure is applied to refractive index sensors, resulting in a type with a sensitivity of 2740 nm/RIU and a figure of merit of 52.69. Full article

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18 pages, 4126 KiB

Open AccessArticle

Exploring the Influence of the Illumination and Painting Tone of Art Galleries on Visual Comfort

by Yue Feng, Zhisheng Wang, Manqun Zhang, Xinjing Qin and Ting Liu

Photonics 2022, 9(12), 981; https://doi.org/10.3390/photonics9120981 - 14 Dec 2022

Cited by 1 | Viewed by 1774

Abstract

Because of the increase in green lighting in recent years, scholars have been trying to find more comfortable lighting methods in various fields to meet people’s lighting needs. In previous studies, we found that most museum lighting was conducted in the form of [...] Read more.

Because of the increase in green lighting in recent years, scholars have been trying to find more comfortable lighting methods in various fields to meet people’s lighting needs. In previous studies, we found that most museum lighting was conducted in the form of subjective questionnaires, but in this study, we tried to introduce a new way to explore the impact of the lighting environment on comfort, namely eye tracking technology. This paper aims to explore the influences when viewing paintings in cold, warm, and middle tones under illumination of 50 lx, 150 lx, and 300 lx, respectively, on the visual comfort of viewers, and the use visual fatigue as the evaluation index to find the most appropriate illumination value for different painting systems in the art museum. By collecting eye movement data under different illuminance and color combination of different paintings and subjective evaluation from the subjects, this paper studies the impact of different illuminances and colors on the subjects’ visual fatigue. By considering the illumination intensity of the light environment and the tone of the painting, it can be found that the warm tone painting was more suitable for 150 lx, the cold tone painting was more suitable for 50 lx, and the middle tone painting was more suitable for 300 lx. Full article

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9 pages, 2104 KiB

Open AccessCommunication

A Simple Photonic System for DFS and AOA Simultaneous Measurement

by Xintong Li, Jinming Tao, Jinye Li, Qianqian Jia, Chaoquan Wang and Jianguo Liu

Photonics 2022, 9(12), 980; https://doi.org/10.3390/photonics9120980 - 14 Dec 2022

Cited by 4 | Viewed by 1822

Abstract

A simple photonics-based dual-channel system is proposed to simultaneously measure the Doppler frequency shift (DFS) and angle of arrival (AOA) of microwave signals. The system applies two parallel push–pull Mach–Zehnder modulators (MZMs) for carrier suppression dual-sideband (CS-DSB) modulation. The introduction of the reference [...] Read more.

A simple photonics-based dual-channel system is proposed to simultaneously measure the Doppler frequency shift (DFS) and angle of arrival (AOA) of microwave signals. The system applies two parallel push–pull Mach–Zehnder modulators (MZMs) for carrier suppression dual-sideband (CS-DSB) modulation. The introduction of the reference signal results in a DFS measurement without direction ambiguity. The DFS can be determined by measuring the frequency of the down-converted intermediate frequency (IF) signal, and the AOA can be calculated by comparing the phase shift of the two channels. A proof-of-concept experiment shows that the DFS measurement error is less than 0.4 Hz during ±100 kHz, and the AOA measurement error is within 1.5° in a range of 0–70°. Full article

(This article belongs to the Special Issue Microwave Photonics II)

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15 pages, 3912 KiB

Open AccessArticle

Preparation and Characterization of Nanostructured Inorganic Copper Zinc Tin Sulfide-Delafossite Nano/Micro Composite as a Novel Photodetector with High Efficiency

by Amira H. Ali, Asmaa S. Hassan, Ashour M. Ahmed, Ahmed A. Abdel-Khaliek, Sawsan Abd El Khalik, Safaa M. Abass, Mohamed Shaban, Fatimah Mohammed Alzahrani and Mohamed Rabia

Photonics 2022, 9(12), 979; https://doi.org/10.3390/photonics9120979 - 14 Dec 2022

Cited by 5 | Viewed by 2378

Abstract

A novel photodetector, based on Cu₂ZnSnS_4, CZTS, is deposited on Cu/CuFeO₂ for wavelength and light power intensity detection. The preparation of CuFeO₂ is carried out by the direct combustion of Cu foil wetted with Fe(NO₃)₂ [...] Read more.

A novel photodetector, based on Cu₂ZnSnS_4, CZTS, is deposited on Cu/CuFeO₂ for wavelength and light power intensity detection. The preparation of CuFeO₂ is carried out by the direct combustion of Cu foil wetted with Fe(NO₃)₂ solution. The preparation of CZTS is carried out using the hydrothermal method, then it is dropped on CuFeO₂ using the drop casting method at 70 °C. Various analyses are used to look at the chemical, morphological, and optical aspects of the Cu/CuFeO₂/CZTS, such as UV–vis, SEM, TEM, selected-area electron diffraction, and XRD, in which all characteristic peaks are confirmed for the prepared materials. The Cu/CuFeO₂/CZTS thin film’s SEM image has a homogeneous morphology, with particles that are around 350 nm in size, demonstrating a significant improvement in morphology over Cu/CuFeO₂/CZTS thin film. The TEM analysis verified the nanostructured morphology of Cu/CuFeO₂/CZTS. From XRD analysis of Cu/CuFeO₂/CZTS, the high intensity of the generated peaks indexed to hexagonal (2H) CuFeO₂ and kesterite CZTS crystal structures revealed a compact highly crystal material. From optical analysis, CZTS, Cu/CuFeO₂, and Cu/CuFeO₂/CZTS thin films recoded band gaps of 1.49, 1.75, and 1.23 eV, respectively. According to the band gap measurements, the optical absorption of the Cu/CuFeO₂/CZTS photodetector has clearly increased. The Cu/CuFeO₂/CZTS as photodetector has a detectivity (D) and responsivity (R) of 1.7 × 10¹⁰ Jones and 127 mAW⁻¹, respectively. Moreover, the external quantum efficiency (EQE) is 41.5% at 25 mW·cm⁻² and 390 nm. Hence, the prepared Cu/CuFeO₂/CZTS photodetector has a very high photoelectrical response, making it very promising as a broadband photodetector. Full article

(This article belongs to the Special Issue Advances in Avalanche Photodiodes)

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12 pages, 9497 KiB

Open AccessArticle

Simulation on Secondary Electron Multiplication Behavior of the Microchannel Plate under DC Mode

by Fengyan Li, Dongyu Jiang, Peng Jiao, Yong Sun and Yonggang Huang

Photonics 2022, 9(12), 978; https://doi.org/10.3390/photonics9120978 - 13 Dec 2022

Viewed by 2109

Abstract

In this study, a three-dimensional microchannel model of a single hollow-core glass fiber was constructed and the Finite Integral Technique and Monte Carlo method were combined to comprehensively simulate the electron multiplication process in a single channel under DC mode. The electron dynamic [...] Read more.

In this study, a three-dimensional microchannel model of a single hollow-core glass fiber was constructed and the Finite Integral Technique and Monte Carlo method were combined to comprehensively simulate the electron multiplication process in a single channel under DC mode. The electron dynamic trajectory in DC electron emission mode was achieved. The effects of different structural parameters and applied bias voltage on the electron gain and the most probable exit energy at the output end of MCP were investigated. The results show that the electrons with a certain initial current can be continuously and stably multiplied in the channel under DC mode and eventually reach a stable value because of the space charge effect; additionally, the electron gain increases with the increase in the bias angle and DC bias voltage and decreases with the increase in the penetration depth of the MCP output electrode. The electron gain at the output end of the MCP increases with the length-to-diameter ratio under the normalized voltage but shows a maximum value under the constant voltage. The simulation results are consistent with the reported experimental trend and theoretical analyses. The method provides data support for the optimal structural design of the microchannel plate. Full article

(This article belongs to the Topic Progress, Challenges, and Opportunities for Photodetectors)

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14 pages, 2193 KiB

Open AccessArticle

Implementation of Logic Gates in an Erbium-Doped Fiber Laser (EDFL): Numerical and Experimental Analysis

by Samuel Mardoqueo Afanador Delgado, José Luis Echenausía Monroy, Guillermo Huerta Cuellar, Juan Hugo García López and Rider Jaimes Reátegui

Photonics 2022, 9(12), 977; https://doi.org/10.3390/photonics9120977 - 12 Dec 2022

Cited by 2 | Viewed by 1799

Abstract

At a time when miniaturization and optimization of resources are in the foreground, the development of devices that can perform various functions is a primary goal of technological development. In this work, the use of an Erbium-Doped Fiber Laser (EDFL) is proposed as [...] Read more.

At a time when miniaturization and optimization of resources are in the foreground, the development of devices that can perform various functions is a primary goal of technological development. In this work, the use of an Erbium-Doped Fiber Laser (EDFL) is proposed as a basic system for the generation of an optical logic gate. Taking advantage of the dynamic richness of this type of laser and its use in telecommunication systems, the dynamic response is analyzed when the system is perturbed by a digital signal. The emission response of the system is controlled by the intensity of the digital signal, so that it is possible to obtain different logic operations. The numerical results are in good agreement with the experimental observations. The presented work raises new aspects in the use of chaotic systems as a means of obtaining optical logic gates. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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16 pages, 3361 KiB

Open AccessArticle

Light Source Stability Issues and Measurements in Flux Calibrations for Space Gaze Camera

by Cui Lin, Ning Zhang, Tianyi Zhang, Jing Luo, Jianing Zheng and Xiaohui Zhang

Photonics 2022, 9(12), 976; https://doi.org/10.3390/photonics9120976 - 12 Dec 2022

Viewed by 1849

Abstract

Flux calibration is an important test item in laboratory calibration experiments of space gaze cameras, which is the basis for obtaining high-precision scientific application data. In the flux calibration of a space gaze camera, the multi-field calibration method is adopted. The instability of [...] Read more.

Flux calibration is an important test item in laboratory calibration experiments of space gaze cameras, which is the basis for obtaining high-precision scientific application data. In the flux calibration of a space gaze camera, the multi-field calibration method is adopted. The instability of the calibration light source will introduce uncertainty during the calibration process. When the spatial camera adopts the gaze imaging mode, the stability of the light source indicates the change in the total energy received by the image plane during the gaze time, which is characterized by relative uncertainty. When the luminous intensity standard lamp runs for the long-term calibration of the stability of the calibration light source, real-time performance and accuracy cannot be guaranteed. Therefore, it is proposed to use a photodetector to measure the stability of the calibration light source for long-term and real-time accurate measurements. First, the stability of the photodetector is calibrated using the light emitting diode; then, the stability of the calibration light source is measured using the photodetector; finally, the stability uncertainty of the calibration light source and the measurement uncertainty of the method is evaluated. The results of the simulation analysis and experimental verification indicate that the gaze time is 5 min and the sampling frequency of the photodetector is 15 Hz; for example, when the flux calibration time is 8 h, the stability uncertainty of the calibration source is 0.42%, and the relative measurement uncertainty is 0.01%. Full article

(This article belongs to the Special Issue Optical Remote Sensor Design and Development)

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