Photonics

27 pages, 11481 KiB

Open AccessArticle

Polarization-Mode Transformation of the Light Field during Diffraction on Amplitude Binary Gratings

by Pavel A. Khorin, Mariia P. Mamaeva, Yury V. Kapitonov and Svetlana N. Khonina

Photonics 2024, 11(9), 848; https://doi.org/10.3390/photonics11090848 - 6 Sep 2024

Viewed by 165

In this paper, a comparative analysis and numerical simulation of operation of two types of amplitude binary gratings (conventional and fork), both in the focal plane and near-field diffraction under illumination by mode beams with different polarization states, were performed. The simulation of [...] Read more.

In this paper, a comparative analysis and numerical simulation of operation of two types of amplitude binary gratings (conventional and fork), both in the focal plane and near-field diffraction under illumination by mode beams with different polarization states, were performed. The simulation of the field formation in the focal plane was performed using the Richards–Wolf formalism. The diffraction calculation in the near-field diffraction was performed based on the FDTD method, considering the 3D structure of optical elements. The possibility of multiplying the incident beam in different diffraction orders of binary gratings and the polarization transformation associated with spin–orbit interaction at tight focusing were shown. In this case, various polarization transformations were formed in ±1 diffraction orders of the fork grating due to different signs of the introduced vortex-like phase singularity. The obtained results can be useful for the laser processing of materials and surface structuring. Full article

(This article belongs to the Special Issue Recent Advances in Diffractive Optics)

12 pages, 2853 KiB

Open AccessArticle

Research on Mitigating Atmosphere Turbulence Fading by Relay Selections in Free-Space Optical Communication Systems with Multi-Transceivers

by Xiaogang San, Zuoyu Liu and Ying Wang

Photonics 2024, 11(9), 847; https://doi.org/10.3390/photonics11090847 - 6 Sep 2024

Viewed by 170

Abstract

In free-space optical communication (FSOC) systems, atmospheric turbulence can bring about power fluctuations in receiver ends, restricting channel capacity. Relay techniques can divide a long FSOC link into several short links to mitigate the fading events caused by atmospheric turbulence. This paper proposes [...] Read more.

In free-space optical communication (FSOC) systems, atmospheric turbulence can bring about power fluctuations in receiver ends, restricting channel capacity. Relay techniques can divide a long FSOC link into several short links to mitigate the fading events caused by atmospheric turbulence. This paper proposes a Reinforcement Learning-based Relay Selection (RLRS) method based on Deep Q-Network (DQN) in a FSOC system with multiple transceivers, whose aim is to enhance the average channel capacity of the system. Malaga turbulence is studied in this paper. The presence of handover loss is also considered. The relay nodes serve in decode-and-forward (DF). Simulation results demonstrate that the RLRS algorithm outperforms the conventional greedy algorithm, which implies that the RLRS algorithm may be utilized in practical FSOC systems. Full article

(This article belongs to the Special Issue Recent Advances in Optical Turbulence)

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13 pages, 3151 KiB

Open AccessArticle

SuperNANO: Enabling Nanoscale Laser Anti-Counterfeiting Marking and Precision Cutting with Super-Resolution Imaging

by Yiduo Chen, Bing Yan, Liyang Yue, Charlotte L. Jones and Zengbo Wang

Photonics 2024, 11(9), 846; https://doi.org/10.3390/photonics11090846 - 5 Sep 2024

Viewed by 247

Abstract

In this paper, we present a unique multi-functional super-resolution instrument, the SuperNANO system, which integrates real-time super-resolution imaging with direct laser nanofabrication capabilities. Central to the functionality of the SuperNANO system is its capacity for simultaneous nanoimaging and nanopatterning, enabling the creation of [...] Read more.

In this paper, we present a unique multi-functional super-resolution instrument, the SuperNANO system, which integrates real-time super-resolution imaging with direct laser nanofabrication capabilities. Central to the functionality of the SuperNANO system is its capacity for simultaneous nanoimaging and nanopatterning, enabling the creation of anti-counterfeiting markings and precision cutting with exceptional accuracy. The SuperNANO system, featuring a unibody superlens objective, achieves a resolution ranging from 50 to 320 nm. We showcase the instrument’s versatility through its application in generating high-security anti-counterfeiting features on an aluminum film. These ‘invisible’ security features, which are nanoscale in dimension, can be crafted with arbitrary shapes at designated locations. Moreover, the system’s precision is further evidenced by its ability to cut silver nanowires to a minimum width of 50 nm. The integrated imaging and fabricating functions of the SuperNANO make it a pivotal tool for a variety of applications, including nanotrapping, sensing, cutting, welding, drilling, signal enhancement, detection, and nanoscale laser treatment. Full article

(This article belongs to the Special Issue Optical and Photonic Devices: From Design to Nanofabrication)

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21 pages, 8555 KiB

Open AccessArticle

Measured and Predicted Speckle Correlation from Diffractive Metasurface Diffusers

by Sif Fugger, Jonathan Gow, Hongfeng Ma, Villads Egede Johansen and Ulrich J. Quaade

Photonics 2024, 11(9), 845; https://doi.org/10.3390/photonics11090845 - 5 Sep 2024

Viewed by 282

Abstract

Speckles are inherent in structured laser-based light projection using diffractive optics such as metasurfaces or diffractive optical elements (DOEs). One application of structured light is to provide illumination for machine vision and depth sensing. This is particularly attractive for mobile or low-power applications, [...] Read more.

Speckles are inherent in structured laser-based light projection using diffractive optics such as metasurfaces or diffractive optical elements (DOEs). One application of structured light is to provide illumination for machine vision and depth sensing. This is particularly attractive for mobile or low-power applications, where metasurfaces provide a compact, customizable solution, which can furthermore reach extreme field of illuminations. However, the speckles might limit detection capabilities by, e.g., lowering the detection range or providing false results. In this work, we present a series of measurements with matching simulations on a 70 × 50 degrees diffractive diffuser using different light sources (varying divergence angles + VCSEL array) to quantify the impact of speckles. We observe a qualitative agreement in speckle correlation between the measurements and the simulations and explain, in part using cross-correlation for analysis, why we do not observe the same speckle pattern between the measurements and the simulations. By performing extra simulations, we conclude that by only changing the light source, there is a limit to the reduction of the speckle contrast which, we can achieve, and, to reduce it further, alternative approaches such as changing the design method of the diffractive diffuser must be harnessed. Full article

(This article belongs to the Special Issue Recent Advances in Diffractive Optics)

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13 pages, 4228 KiB

Open AccessArticle

Cross-Correlation Algorithm Based on Speeded-Up Robust Features Parallel Acceleration for Shack–Hartmann Wavefront Sensing

by Linxiong Wen, Xiaohan Mei, Yi Tan, Zhiyun Zhang, Fangfang Chai, Jiayao Wu, Shuai Wang and Ping Yang

Photonics 2024, 11(9), 844; https://doi.org/10.3390/photonics11090844 - 5 Sep 2024

Viewed by 192

Abstract

A cross-correlation algorithm to obtain the sub-aperture shifts that occur is a crucial aspect of scene-based SHWS (Shack–Hartmann wavefront sensing). However, when the sub-image is partially absent within the atmosphere, the traditional cross-correlation algorithm can easily obtain the wrong shift results. To overcome [...] Read more.

A cross-correlation algorithm to obtain the sub-aperture shifts that occur is a crucial aspect of scene-based SHWS (Shack–Hartmann wavefront sensing). However, when the sub-image is partially absent within the atmosphere, the traditional cross-correlation algorithm can easily obtain the wrong shift results. To overcome this drawback, we propose an algorithm based on SURFs (speeded-up-robust features) matching. In addition, to meet the speed required by wavefront sensing, CUDA parallel optimization of SURF matching is carried out using a GPU thread execution model and a programming model. The results show that the shift error can be reduced by more than two times, and the parallel algorithm can achieve nearly ten times the acceleration ratio. Full article

(This article belongs to the Special Issue Challenges and Future Directions in Adaptive Optics Technology)

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12 pages, 8816 KiB

Open AccessArticle

A Watt-Level, High-Quality LG_0,±1 Vortex Beam made from a Nd:YVO₄ Laser Pumped by an Annular Beam

by Minghao Guo, Xin Tao, Yueqing Li, Shirui Zhang, Zhenkun Wu, Yuzong Gu and Peng Li

Photonics 2024, 11(9), 843; https://doi.org/10.3390/photonics11090843 - 5 Sep 2024

Viewed by 182

Abstract

In this work, we demonstrate a Watt-level, high-quality Laguerre–Gaussian (LG) LG_0±1 vortex mode directly output from an end-pumped Nd:YVO₄ laser by using an axicon-based annular pump beam. A theoretical model for the annular beam end-pumped solid-state laser with an LG vortex [...] Read more.

In this work, we demonstrate a Watt-level, high-quality Laguerre–Gaussian (LG) LG_0±1 vortex mode directly output from an end-pumped Nd:YVO₄ laser by using an axicon-based annular pump beam. A theoretical model for the annular beam end-pumped solid-state laser with an LG vortex mode output was established. Chirality control of the vortex laser was achieved by carefully tilting the output coupler. Watt-level 1064 nm lasers with pure LG_0,1/LG_0,−1 vortex mode, and the incoherent superposition mode of LG_0,1 odd and even petal modes, were achieved successively in our experiments. The intensity profile of the generated pure LG_0,1 vortex laser was measured, and it can be well fitted by using the standard expression of the LG_0,1 vortex mode. The beam quality of the pure LG_0,1 mode is M_x² = 2.01 and M_y² = 2.00 along the x-axis and y-axis, respectively. Our study demonstrates that that axicon-based annular pumping has great potential in developing high-power vortex solid-state lasers with simple and compact structures. Full article

(This article belongs to the Special Issue Optical Vortex Laser)

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12 pages, 2046 KiB

Open AccessCommunication

Tunable Characteristics of Wedge Plasmonic Waveguide with Thin Metallic Layers

by Ha Trinh Thi, Duong Nguyen Van, Hieu Dang Van and Hoang Manh Chu

Photonics 2024, 11(9), 842; https://doi.org/10.3390/photonics11090842 - 5 Sep 2024

Viewed by 208

Abstract

In this study, we propose a mechanism for tuning the modal characteristics of a wedge plasmonic waveguide. The wedge plasmonic waveguide is composed of a thin metallic layer deposited on a wedge-shaped dielectric waveguide. The tuning mechanism is based on controlling the surface [...] Read more.

In this study, we propose a mechanism for tuning the modal characteristics of a wedge plasmonic waveguide. The wedge plasmonic waveguide is composed of a thin metallic layer deposited on a wedge-shaped dielectric waveguide. The tuning mechanism is based on controlling the surface plasmon polariton (SPP) mode at the interface between the metal layer and the dielectric waveguide instead of controlling the SPP mode at the interface between the wedge-shaped metal layer and the surrounding media. This mechanism is performed by modulating the effective refractive index of the dielectric waveguide using a closely coupled tuning waveguide. The numerically investigated results show that the propagation length of the device can be tuned more than 100%; this characteristic has not been explored yet in previous studies. The effective mode area with deep-subwavelength size is almost kept constant while tuning the propagation length. This study offers new insights into tailoring the modal characteristics of plasmonic waveguides based on controlling the mode property at the interface between the metal layer and the dielectric waveguide. This study is also a guideline for developing active plasmonic devices such as tunable nanoscale lightwave guiding waveguides and THz optic modulators. Full article

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

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19 pages, 5780 KiB

Open AccessReview

Fluorometric Mercury (II) Detection Using Heteroatom-Doped Carbon and Graphene Quantum Dots

by Mosayeb Chaghazardi, Soheila Kashanian, Maryam Nazari, Kobra Omidfar, Yvonne Joseph and Parvaneh Rahimi

Photonics 2024, 11(9), 841; https://doi.org/10.3390/photonics11090841 - 5 Sep 2024

Viewed by 272

Abstract

Mercury ion (Hg²⁺) is one of the most toxic pollutants that can exist throughout the environment and be diffused into water, soil, air, and eventually the food chain. Even a very low level of Hg²⁺ diffused in living organisms can [...] Read more.

Mercury ion (Hg²⁺) is one of the most toxic pollutants that can exist throughout the environment and be diffused into water, soil, air, and eventually the food chain. Even a very low level of Hg²⁺ diffused in living organisms can hurt their DNA and cause the permanent damage of the central nervous system and a variety of consequential disorders. Hence, the development of a sensitive and specific method for the detection of Hg²⁺ at trace ranges is extremely important as well as challenging. Fluorometric detection assays based on graphene quantum dots (GQDs) and carbon quantum dots (CQDs) offer considerable potential for the determination and monitoring of heavy metals due to their fascinating properties. Although the quantum yield of GQDs and CQDs is sufficient for their use as fluorescent probes, doping with heteroatoms can significantly improve their optical properties and selectivity toward specific analytes. This review explores the primary advances of CQDs and GQDs in their great electronic, optical, and physical properties, their synthetic methods, and their use in Hg²⁺ fluorimetry detection. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)

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13 pages, 663 KiB

Open AccessArticle

Joint Constellation and Reflectance Optimization for Tunable Intelligent Reflecting Surface-Aided VLC Systems

by Linqiong Jia, Qikai Wang and Yijin Zhang

Photonics 2024, 11(9), 840; https://doi.org/10.3390/photonics11090840 - 5 Sep 2024

Viewed by 202

Abstract

The intelligent reflecting surface (IRS) is an emerging technology that can conquer visible light communication’s (VLC) dependency on the line-of-sight (LoS) channel by offering additional non-light-of-sight (NLoS) communication links. In this paper, a newly proposed electro-tunable intelligent reflecting metasurface is deployed in dimmable [...] Read more.

The intelligent reflecting surface (IRS) is an emerging technology that can conquer visible light communication’s (VLC) dependency on the line-of-sight (LoS) channel by offering additional non-light-of-sight (NLoS) communication links. In this paper, a newly proposed electro-tunable intelligent reflecting metasurface is deployed in dimmable single-input single-output (SISO) VLC systems. We aim to improve the bit error rate (BER) performance by jointly optimizing the transmit constellation and the reflectance of the IRS units. To this end, the optimization problem can be solved in two steps. The minimum distance of the received constellation is firstly maximized by a convex problem, which guarantees the minimum BER. Then, the transmit constellation and the synchronously-tunable reflectance of the IRS units that correspond to the optimal received constellation are determined with an iterative alternate optimization algorithm. Finally, the simulation results show the BER performance improvement and the dimming relaxation benefit of the tunable IRS-aided SISO VLC systems. Full article

(This article belongs to the Special Issue Recent Advances in Optical Wireless Communication Systems and Networks)

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17 pages, 934 KiB

Open AccessArticle

A Grant Report: Examining the Efficacy of Remote Photobiomodulation Therapy in Adolescents with Major Depressive Disorder

by Adriano Alberti, Willians Fernando Vieira, David Richer Araujo Coelho and Daniel Fernandes Martins

Photonics 2024, 11(9), 839; https://doi.org/10.3390/photonics11090839 - 5 Sep 2024

Viewed by 294

Abstract

Major depressive disorder (MDD) is a prevalent mental health condition affecting a significant portion of the population worldwide. This condition can impact individuals of all ages, including adolescents, leading to an impact on various aspects of their lives. Adolescence is a crucial phase [...] Read more.

Major depressive disorder (MDD) is a prevalent mental health condition affecting a significant portion of the population worldwide. This condition can impact individuals of all ages, including adolescents, leading to an impact on various aspects of their lives. Adolescence is a crucial phase of human development, characterized by several neurobiological changes. The onset of MDD during this period can result in damage not only to teenagers but also might have long-lasting implications for their future as adults. Notably, the onset of MDD in adolescents is often associated with various biomarkers, such as increased levels of inflammatory cytokines (e.g., IL-6, TNF-α), oxidative stress markers, and alterations in neurotransmitter levels, indicating a complex interplay of biological factors. Therefore, early intervention is essential for addressing MDD during this phase. Photobiomodulation therapy (PBMT) emerges as an innovative and promising approach that utilizes light, especially in the near-infrared (NIR) and red spectra, to trigger biological and therapeutic effects. Notably, targeting the skull and abdomen with PBMT might explore the bidirectional communication between the intestinal system and the central nervous system in a remote and/or systemic way. In this context, we present the rationale and design of an ongoing study aiming to assess the efficacy of PBMT on depressive symptoms and biomarkers associated with oxidative stress and mitochondrial function in adolescents with MDD. Full article

(This article belongs to the Special Issue Brain Photobiomodulation: Searching for Predictive Target Engagement)

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13 pages, 4947 KiB

Open AccessArticle

Ultra-Compact Reflective Waveguide Mode Converter Based on Slanted-Surface and Subwavelength Metamaterials

by Yanxia Zhang, Rui Feng, Bojian Shi, Xiaoxin Li, Yanyu Gao, Wenya Gao, Qi Jia, Fangkui Sun, Yongyin Cao and Weiqiang Ding

Photonics 2024, 11(9), 838; https://doi.org/10.3390/photonics11090838 - 4 Sep 2024

Viewed by 363

Abstract

Mode converter (MC) is an indispensable element in the mode multiplexing and demultiplexing system. Most previously reported mode converters have been of the transmission type, while reflective mode converters are significantly lacking. In this paper, we propose an ultra-compact reflective mode converter (RMC) [...] Read more.

Mode converter (MC) is an indispensable element in the mode multiplexing and demultiplexing system. Most previously reported mode converters have been of the transmission type, while reflective mode converters are significantly lacking. In this paper, we propose an ultra-compact reflective mode converter (RMC) structure, which comprises a slanted waveguide surface coated with a metallic film and a subwavelength metamaterial refractive index modulation region. The results demonstrate that this RMC can achieve high-performance mode conversion within an extremely short conversion length. In the two-dimensional (2D) case, the conversion length for TE₀–TE₁ is only 810 nm, and the conversion efficiency reaches to 94.1% at the center wavelength of 1.55 μm. In a three-dimensional (3D) case, the TE₀–TE₁ mode converter is only 1.14 μm, with a conversion efficiency of 92.5%. Additionally, for TE₀–TE₂ mode conversion, the conversion size slightly increases to 1.4 μm, while the efficiency reaches 94.2%. The proposed RMC demonstrates excellent performance and holds great potential for application in various integrated photonic devices. Full article

(This article belongs to the Special Issue Advanced Photonics Metamaterials and Metasurfaces: Science and Applications)

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21 pages, 8025 KiB

Open AccessArticle

Design and Characterization of a Portable Multiprobe High-Resolution System (PMHRS) for Enhanced Inversion of Water Remote Sensing Reflectance with Surface Glint Removal

by Shuangkui Liu, Ye Jiang, Kai Wang, Yachao Zhang, Zhe Wang, Xu Liu, Shiyu Yan and Xin Ye

Photonics 2024, 11(9), 837; https://doi.org/10.3390/photonics11090837 - 4 Sep 2024

Viewed by 319

Abstract

Surface glint significantly reduces the measurement accuracy of remote sensing reflectance of water, R_rs, making it difficult to effectively use field measurements for studying water optical properties, accurately retrieving water quality parameters, and validating satellite remote sensing products. To accurately assess [...] Read more.

Surface glint significantly reduces the measurement accuracy of remote sensing reflectance of water, R_rs, making it difficult to effectively use field measurements for studying water optical properties, accurately retrieving water quality parameters, and validating satellite remote sensing products. To accurately assess the effectiveness of various glint removal methods and enhance the accuracy of water reflectance measurements, a portable multiprobe high-resolution System (PMHRS) is designed. The system is composed of a spectrometer, fiber bundles, an irradiance probe, and three radiance probes. The reliability and measurement accuracy of the PMHRS are ensured through rigorous laboratory radiometric calibration and temperature correction. The comprehensive uncertainty of laboratory calibration ranges from 1.29% to 1.43% for irradiance calibration and from 1.47% to 1.59% for radiance calibration. Field measurement results show a strong correlation with both synchronous ASD data, and Sen2Cor-atmospherically corrected Sentinel-2B data (R² = 0.949, RMSE = 0.013; R² = 0.926, RMSE = 0.0105). The water-leaving radiance measurements obtained under different solar elevation angles using three methods (M99 method, polarization method, and SBA) demonstrate that the improved narrow field-of-view polarization probe effectively removes surface glint across various solar elevation angles (with overall better performance than the traditional M99 method). At a solar elevation angle of 69.7°, the MAPD and MAD between the measurements of this method and those of the SBA are 5.8% and 1.4 × 10⁻⁴, respectively. The results demonstrate that the PMHRS system outperforms traditional methods in sun glint removal, significantly enhancing the accuracy of water remote sensing reflectance measurements and improving the validation quality of satellite data. This work provides a crucial technical foundation for the development of high-resolution continuous observation platforms in complex aquatic environments. It holds significant implications for improving the accuracy of field-based water remote sensing reflectance measurements and for enhancing the quality of water ecological monitoring data and satellite validation data. Full article

(This article belongs to the Special Issue Emerging Trends in Spectral Analysis with Optical Sensors: Modern Approaches and Applications)

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13 pages, 4463 KiB

Open AccessArticle

High-Sensitivity SPR Sensor Based on the Theory of the Solution of Inventive Problems

by Cui-lan Zhu, Jin-da Liu and Fang Wang

Photonics 2024, 11(9), 836; https://doi.org/10.3390/photonics11090836 - 4 Sep 2024

Viewed by 230

Abstract

Fiber SPR biosensors have low sensitivity and accuracy in detecting biomolecules. In this study, the TRIZ is applied to molecules and optimization. By defining the prototype system, clarifying the components and interacting objects, and adopting a functional model analysis and causal analysis, we [...] Read more.

Fiber SPR biosensors have low sensitivity and accuracy in detecting biomolecules. In this study, the TRIZ is applied to molecules and optimization. By defining the prototype system, clarifying the components and interacting objects, and adopting a functional model analysis and causal analysis, we deeply explored the key points and root causes of leakage and used a variety of tools, such as technological contradiction, object-field analysis, the HOW-TO model and knowledge effect library, physical contradiction, and the villain method, to come up with different solutions. A novel multimode–single-mode–multimode fiber SPR sensor based on the structure of gold (Au)–molybdenum disulfide (MoS₂)–gold nanoparticles was designed and manufactured by using the TRIZ systematically for the first time. Under the effective guidance of the TRIZ, the sensitivity of the novel sensor is significantly enhanced after the optimization and experimental verification. The new sensor provides an effective reduction in the cost of detection and production and at the same time has excellent stability, ease of preparation, and high reproducibility, which is of significant value and significance for practical applications. Full article

(This article belongs to the Section Lasers, Light Sources and Sensors)

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14 pages, 1065 KiB

Open AccessArticle

Analysis and Selection of the Optimal Pump Laser Power Density for SERF Co-Magnetometer Used in Rotation Sensing

by Kai Zhang, Linlin Yuan, Ze Cai, Hang Gao, Rui Wang, Pengcheng Du and Xinxiu Zhou

Photonics 2024, 11(9), 835; https://doi.org/10.3390/photonics11090835 - 4 Sep 2024

Viewed by 267

Abstract

This paper systematically studies the output noise model of the K-Rb-²¹Ne co-magnetometer and proposes the method for determining the optimal pump laser power density. The amplitude-frequency response and the equivalent model for each frequency band are obtained through the transfer function [...] Read more.

This paper systematically studies the output noise model of the K-Rb-²¹Ne co-magnetometer and proposes the method for determining the optimal pump laser power density. The amplitude-frequency response and the equivalent model for each frequency band are obtained through the transfer function of the co-magnetometer. Based on the established model and considering the power spectral density characteristics of magnetic noise, the output noise equation is formulated. Consequently, the pump laser power density yielding minimal output noise is determined. Both experimental and simulation results indicate that the pump laser power density yielding minimal output noise is greater than the pump laser power density corresponding to the maximum scale factor. Moreover, when the co-magnetometer operates at the pump laser power density corresponding to the minimal output noise, the output noise can be reduced by approximately 25%, and the Allan variance reaches its optimal value. The optimal Allan variance at 180 °C and 190 °C are 0.01395°/h @100 s and 0.01329°/h @100 s, respectively. Therefore, this pump laser power density is designated as the optimal pump laser power density for the co-magnetometer. Finally, simulations are conducted to investigate the variation patterns of the optimal pump laser power density points and the minimum output noise under different density ratios and gas pressures. The theories and methods proposed in this paper provide significant reference value for selecting the optimal pump laser power density and suppressing magnetic noise in co-magnetometers. Full article

(This article belongs to the Special Issue Quantum Enhanced Devices and Instruments for Sensing Applications)

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9 pages, 2255 KiB

Open AccessArticle

A Microwave Photonic Channelized Receiver Based on Polarization-Division Multiplexing of Optical Signals

by Bo Chen, Jingyi Wang, Yankun Li, Jiajun Tan, Changhui Liang and Qunfeng Dong

Photonics 2024, 11(9), 834; https://doi.org/10.3390/photonics11090834 - 3 Sep 2024

Viewed by 371

Abstract

Aimed at the problems of optical frequency combs, such as their large number of comb lines, their high flatness, and their lack of ease in generating, as well as the fact that the channelization efficiency of the scheme based on optical frequency combs [...] Read more.

Aimed at the problems of optical frequency combs, such as their large number of comb lines, their high flatness, and their lack of ease in generating, as well as the fact that the channelization efficiency of the scheme based on optical frequency combs is low, we proposed a microwave photonic channelization receiver based on signal polarization multiplexing. Using two-line local optical frequency combs with different frequencies to demodulate the RF signal in the orthogonal polarization state, 16 sub-channels with a bandwidth of 1 GHz can be received simultaneously. The experimental results show that the image rejection ratio can reach 28 dB, and the third-order spurious-free dynamic range of the system can reach 96.8 dB·Hz^2∕3. This scheme has the advantages of a large number of sub-channels and a high channelization efficiency; it has great application potential in broadband wireless communication, radar, and electronic warfare systems. Full article

(This article belongs to the Special Issue New Perspectives in Microwave Photonics)

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6 pages, 180 KiB

Open AccessEditorial

Optical Technologies Supporting 5G/6G Mobile Networks

by Zbigniew Zakrzewski, Mariusz Głąbowski, Piotr Zwierzykowski, Vincenzo Eramo and Francesco Giacinto Lavacca

Photonics 2024, 11(9), 833; https://doi.org/10.3390/photonics11090833 - 3 Sep 2024

Viewed by 386

Abstract

Intensively developed mobile systems and networks 5G [...] Full article

(This article belongs to the Special Issue Optical Technologies Supporting 5G/6G Mobile Networks)

10 pages, 542 KiB

Open AccessArticle

An Efficient Hybrid Method for Calculating the Focal Field of a Cassegrain Antenna

by Hongfei Lian, Yanwen Jiang, Dawei Lu, Huaitie Xiao and Hongqi Fan

Photonics 2024, 11(9), 832; https://doi.org/10.3390/photonics11090832 - 3 Sep 2024

Viewed by 287

Abstract

The evaluation of the focal field of Cassegrain antennas is crucial for the design and optimization of the complex feeds in quasi-optical systems. However, employing traditional physical optics methods generates high computational complexity and is inefficient. An accurate and efficient calculation method of [...] Read more.

The evaluation of the focal field of Cassegrain antennas is crucial for the design and optimization of the complex feeds in quasi-optical systems. However, employing traditional physical optics methods generates high computational complexity and is inefficient. An accurate and efficient calculation method of Cassegrain antennas’ focal fields that involves a range of incidence angles is proposed, which integrates ray tracing and vector diffraction integration (RT-VDI) theories. It can calculate the focal field in any given or predefined incident direction, not limited to the case of axial incidence. In addition, the use of the equivalent parabolic theory greatly simplifies the process of integral calculation. Moreover, ray tracing and integration operations are executed upon the calculation of the reflector to further improve efficiency. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method. Full article

(This article belongs to the Special Issue The Emerging Science and Applications of Fiber Laser Technology)

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7 pages, 1455 KiB

Open AccessArticle

A Novel Electromagnetic Wavelength Measurement Method Based on Photoacoustic Effect and Photoacoustic Response Characteristics of Nanomaterials

by Yijie Huang, Renbin Zhong, Zhenhui Zhang and Lin Huang

Photonics 2024, 11(9), 831; https://doi.org/10.3390/photonics11090831 - 2 Sep 2024

Viewed by 279

Abstract

This study proposes a differential wavelength measurement method based on the electromagnetic-induced photoacoustic effect. The differential method involves irradiating the sample with multiple wavelengths and utilizing differences in absorption characteristics across different materials to calculate and measure the excitation light wavelengths. Compared to [...] Read more.

This study proposes a differential wavelength measurement method based on the electromagnetic-induced photoacoustic effect. The differential method involves irradiating the sample with multiple wavelengths and utilizing differences in absorption characteristics across different materials to calculate and measure the excitation light wavelengths. Compared to traditional detection methods, this approach combines the unique properties of electromagnetic-induced photoacoustic effect, offering high sensitivity and a wider detection range from microwave to light. Furthermore, the system is structurally simple and stable, suitable for non-destructive testing of various materials, including wavelength-sensitive biological tissues. The experimental results demonstrate that combined with Polymers Benzodithiophene Triazole–Quinoxaline (PBTQ) and Single-Walled Carbon Nanotubes (SWCNTs) as absorbing media, this technique provides a rapid and cost-effective means of wavelength measurement, achieving an uncertainty of approximately 2.33 nm within the range of 680–800 nm, and it can be used for wavelength/frequency measurement of various electromagnetic waves. Full article

(This article belongs to the Special Issue New Perspectives in Biomedical Optics and Optical Imaging)

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27 pages, 4033 KiB

Open AccessArticle

Survey on Optical Wireless Communication with Intelligent Reflecting Surfaces

by Chengwei Fang, Shuo Li, Yinong Wang and Ke Wang

Photonics 2024, 11(9), 830; https://doi.org/10.3390/photonics11090830 - 2 Sep 2024

Viewed by 308

Abstract

Optical Wireless Communication (OWC) technology has gained significant attention in recent years due to its potential for providing high-data-rate wireless connections through the large license-free bandwidth available. A key challenge in OWC systems, similar to high-frequency Radiofrequency (RF) systems, is the presence of [...] Read more.

Optical Wireless Communication (OWC) technology has gained significant attention in recent years due to its potential for providing high-data-rate wireless connections through the large license-free bandwidth available. A key challenge in OWC systems, similar to high-frequency Radiofrequency (RF) systems, is the presence of dead zones caused by obstacles like buildings, trees, and moving individuals, which can degrade signal quality or disrupt data transmission. Traditionally, relays have been used to mitigate these issues. Intelligent Reflecting Surfaces (IRSs) have recently emerged as a promising solution, enhancing system performance and flexibility by providing reconfigurable communication channels. This paper presents an overview of the application of IRSs in OWC systems. Specifically, we categorize IRSs into two main types: mirror array-based IRSs and metasurface-based IRSs. Furthermore, we delve into modeling approaches of mirror array-based IRSs in OWC and analyze recent advances in IRS control, which are classified into system power or gain optimization-oriented, system link reliability optimization-oriented, system data rate optimization-oriented, system security optimization-oriented, and system energy optimization-oriented approaches. Moreover, we present the principles of metasurface-based IRSs from a physical mechanism perspective, highlighting their application in OWC systems through the distinct roles of light signal refraction and reflection. Finally, we discuss the key challenges and potential future directions for integrating IRS with OWC systems, providing insights for further research in this promising field. Full article

(This article belongs to the Special Issue Advancements in Wireless Optical Communication: Integrating Visible Light and Beyond)

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14 pages, 4065 KiB

Open AccessArticle

The Improvement of Luminous Uniformity of Large-Area Organic Light-Emitting Diodes by Using Auxiliary Electrodes

by Fuh-Shyang Juang, Jia-You Chen, Wen-Kai Kuo and Krishn Das Patel

Photonics 2024, 11(9), 829; https://doi.org/10.3390/photonics11090829 - 2 Sep 2024

Viewed by 255

Abstract

The study developed a large emission area of flexible blue organic light-emitting diodes (BOLED) on a polyethylene terephthalate/ Indium tin oxide (PET/ITO) substrate using a polycyclic skeleton ν-DABNA Thermally Activated Delayed Fluorescence (TADF) material. Initially, a 1 × 1 cm² blue OLED [...] Read more.

The study developed a large emission area of flexible blue organic light-emitting diodes (BOLED) on a polyethylene terephthalate/ Indium tin oxide (PET/ITO) substrate using a polycyclic skeleton ν-DABNA Thermally Activated Delayed Fluorescence (TADF) material. Initially, a 1 × 1 cm² blue OLED was fabricated to optimize the layer thickness. The blue OLED structure consisted of PET/ITO/HATCN/TAPC/UBH-21:ν-DABNA/TPBi/LiF/Al. However, as the emission area increased to 3.5 × 3.5 cm², the current density decreased due to the resistance of PET/ITO, leading to luminance non-uniformity. To address this issue, auxiliary Au lines were added to the ITO anode to enhance current injection. Despite this, when the Au lines reached a thickness of 30 nm, average light emission was disrupted. To improve the luminescence characteristics of large-area PET/ITO OLEDs, a capping and planarization layer of PEDOT:PSS was applied. Grid uniformity revealed a significant increase in overall luminance uniformity from 74.1% to 87.4% with the addition of auxiliary Au lines. Further increases in grid line density slightly reduced uniformity but enhanced brightness, resulting in brighter, flexible, large-area blue OLED lighting panels. Full article

(This article belongs to the Special Issue Organic Light-Emitting Diodes: Recent Breakthroughs and Future Directions)

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13 pages, 2552 KiB

Open AccessArticle

Fundamentals of Determination of the Biological Tissue Refractive Index by Ellipsoidal Reflector Method

by Natalia Bezugla, Oleksandra Romodan, Pawel Komada, Nataliia Stelmakh and Mykhailo Bezuglyi

Photonics 2024, 11(9), 828; https://doi.org/10.3390/photonics11090828 - 2 Sep 2024

Viewed by 339

Abstract

This paper presents the theoretical fundamentals, prerequisites for creation, and peculiarities of modeling a new method for determining the refractive index of biological tissues. The method uses a mirror ellipsoid of revolution as an optical element to ensure total internal reflection phenomena. This [...] Read more.

This paper presents the theoretical fundamentals, prerequisites for creation, and peculiarities of modeling a new method for determining the refractive index of biological tissues. The method uses a mirror ellipsoid of revolution as an optical element to ensure total internal reflection phenomena. This paper thoroughly analyzes the differences in the refractive index of healthy and pathological tissues on a biometric diagnostic basis. The analysis is used to model the measurement setup’s parameters. This paper also considers various methods of determining the refractive index of biological tissues based on different principles of physical optics, such as interferometry, refractometry, ellipsometry, and goniophotometry. It systematizes typical optical elements of total internal reflection that can be used in goniophotometry. It justifies the selection of the element base for the goniometric installation based on the ellipsoidal reflector method. A simulation of the installation operation was carried out for various parameters of the ellipsoidal reflector, ensuring the measurement of the biological tissue refractive index from 1.33 to 1.7. This paper also proposes a constructive solution for manufacturing an ellipsoidal reflector of the required configuration. Full article

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14 pages, 4164 KiB

Open AccessArticle

Increasing Light-Induced Forces with Magnetic Photonic Glasses

by Hugo Avalos-Sánchez, Abraham J. Carmona-Carmona, Martha A. Palomino-Ovando, Benito Flores Desirena, Rodolfo Palomino-Merino, Khashayar Misaghian, Jocelyn Faubert, Miller Toledo-Solano and Jesus Eduardo Lugo

Photonics 2024, 11(9), 827; https://doi.org/10.3390/photonics11090827 - 1 Sep 2024

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Abstract

In this work, we theoretically and experimentally study the induction of electromagnetic forces in an opal-based magnetic photonic glass, where light normally impinges onto a disordered arrangement of SiO₂ spheres by the aggregation of Fe₃O₄ nanoparticles. The working wavelength [...] Read more.

In this work, we theoretically and experimentally study the induction of electromagnetic forces in an opal-based magnetic photonic glass, where light normally impinges onto a disordered arrangement of SiO₂ spheres by the aggregation of Fe₃O₄ nanoparticles. The working wavelength is 633 nm. Experimental evidence is presented for the force that results from forced oscillations of the photonic structure. Finite-element method simulations and a theoretical model estimate the magnetic force volumetric density value, peak displacement, and velocity of oscillations. The magnetic force is of the order of 56 microN, which is approximately 500-times higher than forces induced in dielectric optomechanical photonic crystal cavities. Full article

(This article belongs to the Special Issue Emerging Trends in Photonic Crystals)

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18 pages, 6131 KiB

Open AccessArticle

Quantum-Dash Semiconductor Optical Amplifier for Millimeter-Wave over Fibre Wireless Fronthaul Systems

by Xiaoran Xie, Youxin Mao, Chunying Song, Zhenguo Lu, Philip J. Poole, Jiaren Liu, Mia Toreja, Yang Qi, Guocheng Liu, Daniel Poitras, Penghui Ma, Pedro Barrios, John Weber, Ping Zhao, Martin Vachon, Mohamed Rahim, Xianling Chen, Ahmad Atieh, Xiupu Zhang and Jianping Yao

Photonics 2024, 11(9), 826; https://doi.org/10.3390/photonics11090826 - 1 Sep 2024

Viewed by 331

Abstract

This paper demonstrates a five-layer InAs/InP quantum-dash semiconductor optical amplifier (QDash-SOA), which will be integrated into microwave-photonic on-chip devices for millimeter-wave (mmWave) over fibre wireless networking systems. A thorough investigation of the QDash-SOA is conducted regarding its communication performance at different temperatures, bias [...] Read more.

This paper demonstrates a five-layer InAs/InP quantum-dash semiconductor optical amplifier (QDash-SOA), which will be integrated into microwave-photonic on-chip devices for millimeter-wave (mmWave) over fibre wireless networking systems. A thorough investigation of the QDash-SOA is conducted regarding its communication performance at different temperatures, bias currents, and input powers. The investigation shows a fibre-to-fibre (FtF) small-signal gain of 18.79 dB and a noise figure of 6.3 dB. In a common application with a 300 mA bias current and 25 °C temperature, the peak FtF gain is located at 1507.8 nm, which is 17.68 dB, with 3 dB gain bandwidth of 56.6 nm. Furthermore, the QDash-SOA is verified in a mmWave radio-over-fibre link with QAM (32 Gb/s 64-QAM 4-GBaud) and OFDM (250 MHz 64-QAM) signals. The average error vector magnitude of the QAM and OFDM signals after a 2 m wireless link could be as low as 8.29% and 6.78%, respectively. These findings highlight the QDash-SOA’s potential as a key amplifying component in future integrated microwave-photonic on-chip devices. Full article

(This article belongs to the Section Optical Communication and Network)

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16 pages, 2550 KiB

Open AccessArticle

A Study on the Improvement of YOLOv5 and the Quality Detection Method for Cork Discs

by Liguo Qu, Guohao Chen, Ke Liu and Xin Zhang

Photonics 2024, 11(9), 825; https://doi.org/10.3390/photonics11090825 - 1 Sep 2024

Viewed by 355

Abstract

Combining machine vision and deep learning, optical detection technology can achieve intelligent inspection. To address the issues of low efficiency and poor consistency in the quality classification of cork discs used for making badminton heads, research on optimizing the YOLOv5 image-processing algorithm was [...] Read more.

Combining machine vision and deep learning, optical detection technology can achieve intelligent inspection. To address the issues of low efficiency and poor consistency in the quality classification of cork discs used for making badminton heads, research on optimizing the YOLOv5 image-processing algorithm was conducted and applied to cork disc quality detection. Real-time images of cork discs were captured using industrial cameras, and a dataset was independently constructed. A GAN-based defect synthesis algorithm was employed to resolve the lack of defect samples. An attention mechanism was embedded in the YOLOv5 backbone network to enhance feature representation. The number of anchors in the YOLOv5 detection layer was reduced to address similar sample sizes, a center-matching strategy was designed to balance positive samples, and a shortest-distance label assignment algorithm was developed to eliminate ambiguities, improving accuracy and reducing postprocessing complexity. Detection results were integrated into quality classification. Experiments on the NVIDIA RTX3080 GPU demonstrated that the optimized algorithm improved the original YOLOv5 F1 score by 2.4% and mF1 score by 9.0%, achieving a quality classification F1 score of 95.1%, a processing speed of 178.5 FPS, and an mAP of 81.5%. Comparative experiments showed that the improved algorithm achieved the best detection accuracy on the cork disc dataset while maintaining high processing speed. Full article

(This article belongs to the Special Issue Optical Sensing Technologies, Devices and Their Data Applications)

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13 pages, 3639 KiB

Open AccessArticle

Design of Compact Dielectric Metalens Visor for Augmented Reality Using Spin-Dependent Supercells

by Yangyang Li, Jinzhong Ling, Jinkun Guo, Qiang Li, Dihang Zhong and Xiaorui Wang

Photonics 2024, 11(9), 824; https://doi.org/10.3390/photonics11090824 - 1 Sep 2024

Viewed by 359

Abstract

Augmented reality overlays computer-generated virtual information onto real-world scenes, enhancing user interaction and perception. However, traditional augmented reality optical systems are usually large, bulky, and have limited optical performance. In this paper, we propose a novel compact monochrome reflective dielectric metalens visor with [...] Read more.

Augmented reality overlays computer-generated virtual information onto real-world scenes, enhancing user interaction and perception. However, traditional augmented reality optical systems are usually large, bulky, and have limited optical performance. In this paper, we propose a novel compact monochrome reflective dielectric metalens visor with see-through properties, engineered using a periodic structure of spin-dependent supercells. The supercell, which is composed of staggered twin nanofins, provides spin-dependent destructive or constructive interference with different circularly polarized incidences. The design combines the principles of interference with the Pancharatnam–Berry phase to enhance reflection at a working wavelength of 650 nm while maintaining good transmission. Right circularly polarized light incident from the substrate side causes destructive interference, enabling the supercell to work in reflection mode, while left circularly polarized light causes constructive interference, enabling the supercell to work in transmission mode. Furthermore, the supercell-constructed metalens can achieve near-diffraction-limited reflective focusing and a broad diagonal field of view of approximately 96°. In addition, compared to transmissive metalens visors, the reflective design eliminates the need for a beam splitter, significantly reducing the size and weight of the system. Our work could facilitate the development of compact and lightweight imaging systems and provide valuable insights for augmented reality near-eye display applications. Full article

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

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18 pages, 2226 KiB

Open AccessArticle

Optically Delaying a Radio Frequency–Linear Frequency-Modulated (RF-LFM) Pulse Using Kerr Comb Carriers and Off-the-Shelf Concatenation of a Linearly Chirped Fiber Bragg Grating and a Chirped-and-Sampled Fiber Bragg Grating

by Ahmed Almaiman, Yinwen Cao, Peicheng Liao, Alan Willner and Moshe Tur

Photonics 2024, 11(9), 823; https://doi.org/10.3390/photonics11090823 - 31 Aug 2024

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Abstract

We demonstrate a low latency delay of a radio frequency (RF)–linear frequency-modulated (LFM) pulse by modulating it onto optical carriers from a Kerr comb and sending the signal through a concatenation of off-the-shelf linearly chirped fiber Bragg gratings (LC-FBGs) and chirped-and-sampled FBG (CS-FBG). [...] Read more.

We demonstrate a low latency delay of a radio frequency (RF)–linear frequency-modulated (LFM) pulse by modulating it onto optical carriers from a Kerr comb and sending the signal through a concatenation of off-the-shelf linearly chirped fiber Bragg gratings (LC-FBGs) and chirped-and-sampled FBG (CS-FBG). We characterize the frequency response and latency of the LC-FBG and CS-FBG. Then, experimentally, the LFM pulse performance is characterized by measuring the peak sidelobe level (PSL) at the output of the tunable delay system. The experiment, performed with an LFM pulse of 1 GHz bandwidth at a 10 GHz center frequency, shows a PSL better than 34.4 dB, attesting to the high quality of the buffer RF transfer function. Thus, the proposed optical memory buffer architecture, utilizing compact devices based on a Kerr comb and FBGs, offers several benefits for delaying LFM pulses, including (i) a larger tunable delay range, (ii) low latency, (iii) wide bandwidth, and (iv) high PSL. Full article

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

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5 pages, 614 KiB

Open AccessOpinion

The Centration Dilemma in Refractive Corrections: Why Is It Still a Dilemma and How to Cope?

by Samuel Arba Mosquera and Shwetabh Verma

Photonics 2024, 11(9), 822; https://doi.org/10.3390/photonics11090822 - 30 Aug 2024

Viewed by 382

Abstract

(1) Background: Defining the optimum center for laser refractive corrections is difficult, with many of the available approaches having pros and cons. Decentered ablations result in undesirable side effects like halos, glare, monocular diplopia, and a reduction in visual acuity; (2) Methods: The [...] Read more.

(1) Background: Defining the optimum center for laser refractive corrections is difficult, with many of the available approaches having pros and cons. Decentered ablations result in undesirable side effects like halos, glare, monocular diplopia, and a reduction in visual acuity; (2) Methods: The ideal centration in refractive corrections should fulfil three requirements: covering a scotopic pupil; respecting the visual axis; and minimizing tissue removal. The implications of different centration strategies are discussed and shown graphically; (3) Results: Oversized asymmetric offset ablation faces fewer difficulties in registering static cyclotorsion, features less tissue wastage compared to a symmetric offset, and includes a certain amount of coma (and trefoil) in the profile, benefiting eyes with a pupil offset, which typically present with relevant amounts of coma and trefoil corneal aberrations due to decentered optics; (4) Conclusions: There is a need for a flexible choice of centration in refractive procedures to design customized and non-customized treatments optimally. An ideal optical zone covering the pupil with the widest entrance may be as important as a centration reference. Full article

(This article belongs to the Special Issue Visual Optics)

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16 pages, 3639 KiB

Open AccessArticle

Time-of-Flight Camera Intensity Image Reconstruction Based on an Untrained Convolutional Neural Network

by Tian-Long Wang, Lin Ao, Na Han, Fu Zheng, Yan-Qiu Wang and Zhi-Bin Sun

Photonics 2024, 11(9), 821; https://doi.org/10.3390/photonics11090821 - 30 Aug 2024

Viewed by 539

Abstract

With the continuous development of science and technology, laser ranging technology will become more efficient, convenient, and widespread, and it has been widely used in the fields of medicine, engineering, video games, and three-dimensional imaging. A time-of-flight (ToF) camera is a three-dimensional stereo [...] Read more.

With the continuous development of science and technology, laser ranging technology will become more efficient, convenient, and widespread, and it has been widely used in the fields of medicine, engineering, video games, and three-dimensional imaging. A time-of-flight (ToF) camera is a three-dimensional stereo imaging device with the advantages of small size, small measurement error, and strong anti-interference ability. However, compared to traditional sensors, ToF cameras typically exhibit lower resolution and signal-to-noise ratio due to inevitable noise from multipath interference and mixed pixels during usage. Additionally, in environments with scattering media, the information about objects gets scattered multiple times, making it challenging for ToF cameras to obtain effective object information. To address these issues, we propose a solution that combines ToF cameras with single-pixel imaging theory. Leveraging intensity information acquired by ToF cameras, we apply various reconstruction algorithms to reconstruct the object’s image. Under undersampling conditions, our reconstruction approach yields higher peak signal-to-noise ratio compared to the raw camera image, significantly improving the quality of the target object’s image. Furthermore, when ToF cameras fail in environments with scattering media, our proposed approach successfully reconstructs the object’s image when the camera is imaging through the scattering medium. This experimental demonstration effectively reduces the noise and direct ambient light generated by the ToF camera itself, while opening up the potential application of ToF cameras in challenging environments, such as scattering media or underwater. Full article

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14 pages, 3670 KiB

Open AccessArticle

Novel THz Metasurface Biosensor for High-Sensitivity Detection of Vitamin C and Vitamin B9

by Ningyi Wang, Bingwei Liu, Xu Wu and Yan Peng

Photonics 2024, 11(9), 820; https://doi.org/10.3390/photonics11090820 - 30 Aug 2024

Viewed by 404

Abstract

Vitamin C (VC) and Vitamin B9 (VB9) are essential micronutrients integral to numerous biological functions and critical for maintaining human health. The rapid detection of these vitamins is important for verifying nutritional supplements and aiding in clinical diagnoses. This study combined terahertz time-domain [...] Read more.

Vitamin C (VC) and Vitamin B9 (VB9) are essential micronutrients integral to numerous biological functions and critical for maintaining human health. The rapid detection of these vitamins is important for verifying nutritional supplements and aiding in clinical diagnoses. This study combined terahertz time-domain spectroscopy (THz-TDS) with metasurface technology to develop a fast, sensitive, and non-destructive detection method for VC and VB9. Firstly, we determined the characteristic absorption peaks and molecular vibration modes of VC and VB9 within the 0.5–4.0 THz range through quantum chemical calculation and THz-TDS measurement. Then, we designed and fabricated a metasurface biosensor to match its resonance peak with the communal peak of VC and VB9, enhancing the interaction between THz waves and these vitamins. Using this biosensor, we analyzed solutions with different concentrations of VC and VB9. An increase in vitamin concentrations resulted in frequency shifts in the THz resonance peak. Quantifiable relationships between frequency shifts and the vitamin concentrations were established. The detection limits achieved were 158.82 ng/µL for VC and 353.57 ng/µL for VB9, respectively. This method not only demonstrates high sensitivity but also simplifies the operational process, offering an innovative tool for applications in food safety monitoring and clinical diagnostics. Full article

(This article belongs to the Section Optical Interaction Science)

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17 pages, 2449 KiB

Open AccessArticle

Utilizing States of Polarization in One-Dimensional Corite Codes with Two-Code Keying for Optical Code-Division Multiple Access

by Bih-Chyun Yeh

Photonics 2024, 11(9), 819; https://doi.org/10.3390/photonics11090819 - 30 Aug 2024

Viewed by 323

Abstract

We propose a novel family of codes comprising two mutually orthogonal states of polarization (SOPs) for the spectral encoding of one-dimensional (1D) Corite codes with two-code keying (TCK) for use in the spectral amplitude coding (SAC) of optical code-division multiple access (OCDMA) networks. [...] Read more.

We propose a novel family of codes comprising two mutually orthogonal states of polarization (SOPs) for the spectral encoding of one-dimensional (1D) Corite codes with two-code keying (TCK) for use in the spectral amplitude coding (SAC) of optical code-division multiple access (OCDMA) networks. We design these 1D Corite codes with TCK to create a specific code operation function, an encoding optical transmitter structure, and a decoding optical receiver structure, respectively. In the proposed system, multi-user interference (MUI) can occur due to interference from other simultaneous users. However, we have modified the cross-correlation to cancel out the MUI. Although the proposed system recovers bits successfully, it still suffers from phase-induced intensity noise (PIIN). Our numerical results demonstrate that the proposed system using 1D Corite codes with TCK can support a larger number of simultaneous users than other systems that use 1D CTP codes with TCK, 1D M3 sequence codes, 1D BIBD codes, and 1D BDS codes with TCK. Specifically, the proposed system can support up to 48 simultaneous users, which is a notable improvement. Our numerical results indicate that the proposed system using 1D Corite codes with TCK can achieve a data transmission rate of up to 2.5 Gbps, which is a significant improvement. Full article

(This article belongs to the Special Issue Optical Fiber Communication Systems and Networks)

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Photonics, Volume 11, Issue 9 (September 2024) – 67 articles

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