Journal Description
Photonics
Photonics
is an international, scientific, peer-reviewed, open access journal on the science and technology of optics and photonics, published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 15.5 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Companion journal: Optics.
Impact Factor:
2.4 (2022);
5-Year Impact Factor:
2.4 (2022)
Latest Articles
Analysis of Long-Distance Geometric Error Measurement and Uncertainty Based on PSD Laser Collimation Principle
Photonics 2024, 11(6), 538; https://doi.org/10.3390/photonics11060538 - 4 Jun 2024
Abstract
Due to the limitations of traditional geometric error measurement, the measurement accuracy of long-stroke geometric errors is generally not high and the operation is complicated. In response to the above situation, in this study, a geometric error measurement system is built with a
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Due to the limitations of traditional geometric error measurement, the measurement accuracy of long-stroke geometric errors is generally not high and the operation is complicated. In response to the above situation, in this study, a geometric error measurement system is built with a laser beam as the reference line and 2D position sensitive detector as the photoelectric conversion device. The single measurement range is 40 m, and the measurement range is further expanded through the principle of segmented splicing. Using an ultra-long guide rail as the measurement object for straightness measurement, the experimental results are similar to those of a laser interferometer. The uncertainty analysis model was obtained through the analysis of quantity characteristics, and based on this, the variance synthesis theorem and probability distribution propagation principle were studied to form two uncertainty synthesis methods. The measurement evaluation results showed that the two methods were basically consistent. The work provided a reference method for the uncertainty evaluation of position-sensitive detector measurement systems in the future.
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(This article belongs to the Special Issue Advanced Photonic Sensing and Measurement II)
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Open AccessArticle
Integrated Mobile Visible Light Communication and Positioning Systems Based on Decision Feedback Channel Estimation
by
Ruoxuan Wang, Yuzhe Sun, Zhongxu Liu, Mingyi Gao and Xiaodi You
Photonics 2024, 11(6), 537; https://doi.org/10.3390/photonics11060537 - 4 Jun 2024
Abstract
Visible light communication (VLC) and visible light positioning (VLP) systems are usually designed separately to prevent mutual interference, while terminal mobility often introduces challenges that can degrade their performance. In this paper, we propose an integrated visible light communication and positioning (VLCP) scheme
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Visible light communication (VLC) and visible light positioning (VLP) systems are usually designed separately to prevent mutual interference, while terminal mobility often introduces challenges that can degrade their performance. In this paper, we propose an integrated visible light communication and positioning (VLCP) scheme designed for mobile scenarios, encompassing both multiple-input–single-output (MISO) and multiple-input–multiple-output (MIMO) configurations. This scheme integrates both functionalities into a unified system. Utilizing decision feedback channel estimation (DFCE), we effectively estimate the dynamic channel state information (CSI) for both VLC and VLP, thereby potentially enhancing both communication and positioning performance. Simulation results across various routes verify the effectiveness of the proposed scheme. It is observed that when the terminal moves at 1 m/s, the VLCP scheme with DFCE can maintain reliable transmission quality, ensuring bit error rates (BERs) consistently below 1.3 × 10−2. Additionally, the mean positioning errors remain within the centimeter range in different routes, not exceeding 4.3 cm and 15.5 cm in the MISO and MIMO scenarios, respectively.
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(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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Single-Source VLCP System Based on Solar Cell Array Receiver and Right-Angled Tetrahedron Trilateration VLP (RATT-VLP) Algorithm
by
Dawei Xie, Zhongxu Liu and Changyuan Yu
Photonics 2024, 11(6), 536; https://doi.org/10.3390/photonics11060536 (registering DOI) - 4 Jun 2024
Abstract
A significant deployment limitation for visible light communication and positioning (VLCP) systems in energy- and light-source-restricted scenarios is the reliance of photodetectors (PDs) on external power supplies, compromising sustainability and complicating receiver charging. Solar cells (SCs), capable of harvesting and converting environmental light
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A significant deployment limitation for visible light communication and positioning (VLCP) systems in energy- and light-source-restricted scenarios is the reliance of photodetectors (PDs) on external power supplies, compromising sustainability and complicating receiver charging. Solar cells (SCs), capable of harvesting and converting environmental light into electrical energy, offer a promising alternative. Consequently, we first propose an indoor VLCP system that utilizes an SC array as the receiver, alongside a right-angled tetrahedron trilateration visible light positioning (RATT-VLP) algorithm based on a single light source and multiple receivers. The proposed system uses an SC array in place of PDs, utilizing binary phase shift keying (BPSK) signals for simultaneous communication and positioning. In experiments, we verified the system’s error-free communication rate of 1.21 kbps and average positioning error of 3.40 cm in a 30 cm × 30 cm area, indicating that the system can simultaneously satisfy low-speed communication and accurate positioning applications. This provides a viable foundation for further research on SC-based VLCP systems, facilitating potential applications in environments like underwater wireless communication, positioning, and storage tank inspection.
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(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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Open AccessReview
Increase in Modulation Speed of Silicon Photonics Modulator with Quantum-Well Slab Wings: New Insights from a Numerical Study
by
Kensuke Ogawa
Photonics 2024, 11(6), 535; https://doi.org/10.3390/photonics11060535 - 3 Jun 2024
Abstract
A Silicon Photonics modulator is a high-speed photonic integrated circuit for optical data transmission in high-capacity optical networks. Silicon Photonics modulators in the configuration of a Mach–Zehnder interferometer, in which a PN-junction rib-waveguide phase shifter is inserted in each arm of the interferometer,
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A Silicon Photonics modulator is a high-speed photonic integrated circuit for optical data transmission in high-capacity optical networks. Silicon Photonics modulators in the configuration of a Mach–Zehnder interferometer, in which a PN-junction rib-waveguide phase shifter is inserted in each arm of the interferometer, are studied in this paper because of their superior performance of high-quality optical data generation in a wide range of spectral bands and their simplicity in fabrication processes suitable to production in foundries. Design, fabrication, and fundamental characteristics of Silicon Photonics Mach–Zehnder modulators are reviewed as an introduction to these high-speed PICs on the Silicon Photonics platform. Modulation speed, or modulation bandwidth, is a key performance item, as well as optical loss, in the application to high-speed optical transmitters. Limiting factors on modulation speed are addressed in equations. Electrical resistance–capacitance coupling, which causes optical modulation bandwidth–optical loss trade-off, is the most challenging limiting factor that limits high-speed modulation. Expansion of modulation bandwidth is not possible without increasing optical loss in the conventional approaches. A new idea including quantum-mechanical effect in the design of Silicon Photonics modulators is proposed and proved in computational analysis to resolve the bandwidth loss trade-off. By adding high-mobility quantum-well overlayers to the side slab wings of the rib-waveguide phase shifter, the modulation bandwidth is doubled without increasing optical loss to achieve a 200 Gbaud modulation rate.
Full article
(This article belongs to the Special Issue Novel Advances in Integrated Optics)
Open AccessArticle
Generation of Bright–Dark Pulse Pairs in the Er-Doped Mode-Locked Fiber Laser Based on Doped Fiber Saturable Absorber
by
Yaoyao Qi, Qixing Yu, Wei Sun, Yaqing Gao, Yu Zhang, Zhenxu Bai, Jie Ding, Bingzheng Yan, Yulei Wang, Zhiwei Lu and Dapeng Yan
Photonics 2024, 11(6), 534; https://doi.org/10.3390/photonics11060534 - 3 Jun 2024
Abstract
: This study reports new types of passive mode-locked Er-doped fiber laser (EDFL) based on a segment of doped fiber saturable absorber (DFSA) with Tm/Ho-doped fiber (THDF), Yb-doped fiber (YDF), and Er-doped fiber (EDF). By employing THDF-SA, a bright pulse sequence with a
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: This study reports new types of passive mode-locked Er-doped fiber laser (EDFL) based on a segment of doped fiber saturable absorber (DFSA) with Tm/Ho-doped fiber (THDF), Yb-doped fiber (YDF), and Er-doped fiber (EDF). By employing THDF-SA, a bright pulse sequence with a fundamental repetition rate of 17.86 MHz was obtained. In addition, various mode-locked output states, including dark pulses, dark–bright pulse pairs, bright–dark pulse pairs, and second-harmonic pulses, were obtained through polarization modulation and gain modulation, and the orthogonality of dark–bright pulses in both polarization directions was verified. Furthermore, using EDF-SA and YDF-SA, dark pulses and dark–bright pulses were obtained. A comparison of the three experiments revealed that THDF-SA effectively reduces the mode-locked threshold and improves the average output power. Compared with bright pulses, dark pulses offer several advantages such as resisting noise, increasing propagation speed, and suppressing nonlinear scattering (such as pulse-intrinsic Raman scattering); thus, the EDFL can find broad application in long-distance transmission, precision measurement, and other fields.
Full article
(This article belongs to the Special Issue Advanced Lasers and Their Applications II)
Open AccessArticle
In Situ Structural Characterization of Cardiomyocyte Microenvironment by Multimodal STED Microscopy
by
Zhao Zhang, Bruce Z. Gao and Tong Ye
Photonics 2024, 11(6), 533; https://doi.org/10.3390/photonics11060533 - 3 Jun 2024
Abstract
Within the myocardium, cardiomyocytes reside in a complex and dynamic extracellular matrix (ECM) consisting of a basement membrane (BM) and interstitial matrix. The interactions between cardiomyocytes and the myocardial ECM play a critical role in maintaining cardiac geometry and function throughout cardiac development
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Within the myocardium, cardiomyocytes reside in a complex and dynamic extracellular matrix (ECM) consisting of a basement membrane (BM) and interstitial matrix. The interactions between cardiomyocytes and the myocardial ECM play a critical role in maintaining cardiac geometry and function throughout cardiac development and in adult hearts. Understanding how the structural changes of the myocardial ECM affect cardiomyocyte function requires knowledge of pericellular structures. These structures are of a size beyond the resolution of conventional optical microscopy. Here, we demonstrated multi-scale and multi-aspect characterization of the cardiomyocyte microenvironment in myocardial tissue sections using multimodal stimulated emission depletion (STED) microscopy. Second harmonic generation and autofluorescence facilitated multiplexed imaging, enabling the interpretation of protein distribution in 3D. STED imaging modality revealed BM structures of cardiomyocytes and myocardial capillaries at the subdiffractional level. Moreover, meaningful measurements retrieved from acquired images, such as sarcomere length and capillary density, enabled quantitative assessment of myocardial structures.
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(This article belongs to the Special Issue Advanced Optical Microscopy and Imaging Technology)
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Open AccessArticle
Enhancement of Mosquito Collection for Ultraviolet Light-Emitting Diodes Trapping System Using Cavity Reflectors
by
Jui-Chen Chang, Yi-Chian Chen, Wei-Yu Lu, Xuan-Huy Nguyen and Hsiao-Yi Lee
Photonics 2024, 11(6), 532; https://doi.org/10.3390/photonics11060532 - 3 Jun 2024
Abstract
This research explores novel avenues for optimizing mosquito-catching efficiency using a multifaceted approach. While previous studies have primarily focused on singular parameters, such as light intensity or wind speed, this study delves into the intricate interplay between various factors. Experiment 1 challenges conventional
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This research explores novel avenues for optimizing mosquito-catching efficiency using a multifaceted approach. While previous studies have primarily focused on singular parameters, such as light intensity or wind speed, this study delves into the intricate interplay between various factors. Experiment 1 challenges conventional wisdom by revealing a wider light divergence angle. When the reflective plate combined with the airflow board was set to 0 cm in length, the effectiveness of capturing mosquitoes was lower than that of the 3 cm unit, suggesting overlooked variables at play. Experiment 2 introduces a novel perspective by demonstrating the superior efficiency of the 5 cm unit, even with reduced wind speed and luminous area under optimized conditions, showcasing the significance of a holistic approach. Moreover, Experiment 3 uncovers nuanced insights, showcasing the differential performance of units in capturing small insects versus mosquitoes and moths, highlighting the need for tailored strategies. By integrating these findings, the study pioneers the development of two distinct mosquito collection units, emphasizing the critical importance of balancing diverse parameters for optimal results. The innovation lies in the thorough investigation of multifaceted optimization strategies, providing valuable insights to propel advancements in mosquito control technologies.
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(This article belongs to the Special Issue Photodetector Materials and Optoelectronic Devices)
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Open AccessArticle
Independently Accessible Dual-Band Barrier Infrared Detector Using Type-II Superlattices
by
Seung-man Park and Christoph H. Grein
Photonics 2024, 11(6), 531; https://doi.org/10.3390/photonics11060531 - 3 Jun 2024
Abstract
We report a novel dual-band barrier infrared detector (DBIRD) design using InAs/GaSb type-II superlattices (T2SLs). The DBIRD structure consists of back-to-back barrier diodes: a “blue channel” (BC) diode which has an nBp architecture, an n-type layer of a larger bandgap for absorbing the
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We report a novel dual-band barrier infrared detector (DBIRD) design using InAs/GaSb type-II superlattices (T2SLs). The DBIRD structure consists of back-to-back barrier diodes: a “blue channel” (BC) diode which has an nBp architecture, an n-type layer of a larger bandgap for absorbing the blue band infrared/barrier/p-type layer, and a “red channel” (RC) diode which has a pBn architecture, a p-type layer of a smaller bandgap for absorbing the red band infrared/barrier/n-type layer. Each has a unipolar barrier using a T2SL lattice matched to a GaSb substrate to impede the flow of majority carriers from the absorbing layer. Each channel in the DBIRD can be independently accessed with a low bias voltage as is preferable for high-speed thermal imaging. The device modeling of DBIRDs and simulation results of the current–voltage characteristics under dark and illuminated conditions are also presented. They predict that the dual-band operation of the DBIRD will produce low dark currents and 45–56% quantum efficiencies for the in-band photons in the BC with = 5.58 μm, and a nearly constant 32% in the RC with = 8.05 μm. The spectral quantum efficiency of the BC for 500 K blackbody radiation is approximately 50% over the range of = 3–4.7 μm, while that of the RC has a peak of 42% at 5.9 μm. The DBIRD may provide improved high-speed dual-band imaging in comparison with NBn dual-band detectors.
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(This article belongs to the Special Issue Optoelectronic Devices Technologies and Applications)
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Open AccessArticle
A Multi-Parameter Tunable and Compact Plasmon Modulator in the Near-Infrared Spectrum
by
Xuefang Hu, Hongfei Wang, Sisi Yang, Changgui Lu, Xiangyue Zhao and Mengjia Lu
Photonics 2024, 11(6), 530; https://doi.org/10.3390/photonics11060530 - 3 Jun 2024
Abstract
To keep pace with the demands of modern photonic integration technology, the electro-optic modulator should feature multi-parameter tunable components and a compact size. Here, we propose a hybrid structure that can modulate the multi-parameters of surface plasmon polaritons (SPPs) simultaneously with a compact
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To keep pace with the demands of modern photonic integration technology, the electro-optic modulator should feature multi-parameter tunable components and a compact size. Here, we propose a hybrid structure that can modulate the multi-parameters of surface plasmon polaritons (SPPs) simultaneously with a compact size by controlling the electron concentration of indium tin oxide (ITO) in the near-infrared spectrum. The length, width and height of the device are only 15 μm, 5 μm and 9 μm, respectively. The numerical results show that when the electron concentration in ITO changes from 7.5 × 1026 m−3 to 9.5 × 1026 m−3, the variation in amplitude, wavelength and phase are 49%, 300 nm and 347°, respectively. The demonstrated structure paves a new way for multi-parameter modulation and the realization of ultracompact modulators.
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(This article belongs to the Special Issue Advancements in Optical Sensing and Communication Technologies)
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Open AccessArticle
Principles of Measuring Thickness and Refractive Index of Thin Dielectric Film by Using Multiresonance Archimedean Spiral Metasurfaces with C Resonator in the Terahertz Frequency Range
by
Oleg Kameshkov and Vasily Gerasimov
Photonics 2024, 11(6), 529; https://doi.org/10.3390/photonics11060529 - 2 Jun 2024
Abstract
Metasurfaces are an excellent platform for terahertz (THz) sensing applications, enabling highly efficient light–matter interaction and overcoming the fundamental disadvantage of the relatively long-wavelength THz range (30–3000 μm), which limits sensing of small features. The current focus in developing metasurfaces is mostly directed
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Metasurfaces are an excellent platform for terahertz (THz) sensing applications, enabling highly efficient light–matter interaction and overcoming the fundamental disadvantage of the relatively long-wavelength THz range (30–3000 μm), which limits sensing of small features. The current focus in developing metasurfaces is mostly directed toward single-resonance metasurfaces and reconstruction of the dielectric constants of analyte from the saturation mode induced by the limited sensing volume of the metasurface. This paper presents a numerical demonstration of using a multiresonance metasurface to extract the thickness and refractive index of a deposited film without saturation of the sensor. It was shown that the multiresonance property enables determination of the analyte characteristic via measurements with two different thicknesses and tracking changes in two resonances. High-accuracy parameter retrieval is achieved when there are large differences in the thicknesses. In contrast to the established approach, this method provides an efficient way to avoid using relatively thick films.
Full article
(This article belongs to the Special Issue Multifunctional Metasurfaces: Design Strategies and Applications)
Open AccessReview
Far-Field Super-Resolution Microscopy Using Evanescent Illumination: A Review
by
Qianwei Zhang, Haonan Zhang, Xiaoyu Yang, Xu Liu, Mingwei Tang and Qing Yang
Photonics 2024, 11(6), 528; https://doi.org/10.3390/photonics11060528 - 1 Jun 2024
Abstract
The resolution of conventional optical microscopy is restricted by the diffraction limit. Light waves containing higher-frequency information about the sample are bound to the sample surface and cannot be collected by far-field optical microscopy. To break the resolution limit, researchers have proposed various
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The resolution of conventional optical microscopy is restricted by the diffraction limit. Light waves containing higher-frequency information about the sample are bound to the sample surface and cannot be collected by far-field optical microscopy. To break the resolution limit, researchers have proposed various far-field super-resolution (SR) microscopy imaging methods using evanescent waves to transfer the high-frequency information of samples to the low-frequency passband of optical microscopy. Optimization algorithms are developed to reconstruct a SR image of the sample by utilizing the high-frequency information. These techniques can be collectively referred to as spatial-frequency-shift (SFS) SR microscopy. This review aims to summarize the basic principle of SR microscopy using evanescent illumination and introduce the advances in this research area. Some current challenges and possible directions are also discussed.
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(This article belongs to the Special Issue Super Resolution Optical Microscopy: Sensing and Imaging)
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Open AccessArticle
A Terahertz Programmable Digital Metasurface Based on Vanadium Dioxide
by
Tianrui Pan, Chenxi Liu, Shuang Peng, Haiying Lu, Han Zhang, Xiaoming Xu and Fei Yang
Photonics 2024, 11(6), 527; https://doi.org/10.3390/photonics11060527 - 1 Jun 2024
Abstract
Metasurfaces can realize the flexible manipulation of electromagnetic waves, which have the advantages of a low profile and low loss. In particular, the coding metasurface can flexibly manipulate electromagnetic waves through controllable sequence encoding of the coding units to achieve different functions. In
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Metasurfaces can realize the flexible manipulation of electromagnetic waves, which have the advantages of a low profile and low loss. In particular, the coding metasurface can flexibly manipulate electromagnetic waves through controllable sequence encoding of the coding units to achieve different functions. In this paper, a three−layer active coding metasurface is designed based on vanadium dioxide ( ), which has an excellent phase transition. For the designed unit cell, the top patterned layer is composed of two split square resonant rings (SSRRs), whose gaps are in opposite directions, and each SSRR is composed of gold and . When changes from the dielectric state to the metal state, the resonant mode changes from microstrip resonance to LC resonance, correspondingly. According to the Pancharatnam−Berry (P−B) phase, the designed metasurface can actively control terahertz circularly polarized waves in the near field. The metasurface can manipulate the order of the generated orbital angular momentum (OAM) beams: when the dielectric changes to metal , the order l of the OAM beams generated by the metasurface changes from −1 to −2, and the purity of the generated OAM beams is relatively high. It is expected to have important application values in terahertz wireless communication, radar, and other fields.
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(This article belongs to the Special Issue Emerging Trends in Metamaterials and Metasurfaces Research)
Open AccessArticle
Shallow Trench Isolation Patterning to Improve Photon Detection Probability of Single-Photon Avalanche Diodes Integrated in FD-SOI CMOS Technology
by
Shaochen Gao, Duc-Tung Vu, Thibauld Cazimajou, Patrick Pittet, Martine Le Berre, Mohammadreza Dolatpoor Lakeh, Fabien Mandorlo, Régis Orobtchouk, Jean-Baptiste Schell, Jean-Baptiste Kammerer, Andreia Cathelin, Dominique Golanski, Wilfried Uhring and Francis Calmon
Photonics 2024, 11(6), 526; https://doi.org/10.3390/photonics11060526 - 1 Jun 2024
Abstract
The integration of Single-Photon Avalanche Diodes (SPADs) in CMOS Fully Depleted Silicon-On-Insulator (FD-SOI) technology under a buried oxide (BOX) layer and a silicon film containing transistors makes it possible to realize a 3D SPAD at the chip level. In our study, a nanostructurated
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The integration of Single-Photon Avalanche Diodes (SPADs) in CMOS Fully Depleted Silicon-On-Insulator (FD-SOI) technology under a buried oxide (BOX) layer and a silicon film containing transistors makes it possible to realize a 3D SPAD at the chip level. In our study, a nanostructurated layer created by an optimized arrangement of Shallow Trench Isolation (STI) above the photosensitive zone generates constructive interferences and consequently an increase in the light sensitivity in the frontside illumination. A simulation methodology is presented that couples electrical and optical data in order to optimize the STI trenches (size and period) and to estimate the Photon Detection Probability (PDP) gain. Then, a test chip was designed, manufactured, and characterized, demonstrating the PDP improvement due to the STI nanostructuring while maintaining a comparable Dark Count Rate (DCR).
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(This article belongs to the Special Issue Emerging Topics in Single-Photon Detectors)
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Open AccessArticle
A Near Fourier-Limited Pulse-Preserving Monochromator for Extreme-Ultraviolet Pulses in the Few-Fs Regime
by
Yudong Yang, Tanja Neumann, Julia Hengster, Roland E. Mainz, Jakob Elsner, Oliver D. Mücke, Franz X. Kärtner and Thorsten Uphues
Photonics 2024, 11(6), 525; https://doi.org/10.3390/photonics11060525 - 1 Jun 2024
Abstract
We present a pulse-preserving multilayer-based extreme-ultraviolet (XUV) monochromator providing ultra-narrow bandwidth ( , ) and compact footprint ( ) for easy integration into high-harmonic generation (HHG) or free-electron
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We present a pulse-preserving multilayer-based extreme-ultraviolet (XUV) monochromator providing ultra-narrow bandwidth ( , ) and compact footprint ( ) for easy integration into high-harmonic generation (HHG) or free-electron laser (FEL) sources. The temporal resolution of the novel design supports pulse durations of typical pump–probe setups in the femtosecond and attosecond regime, depending on the mirror design and focusing geometries over the tuning range of the monochromator. The theoretical design is analyzed and experimentally characterized in a laser-driven HHG setup.
Full article
(This article belongs to the Special Issue Advances in Ultrafast Optics: From Fundamental Science to Applications)
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Open AccessArticle
A Comprehensive Study on Elasticity and Viscosity in Biomechanics and Optical Properties of the Living Human Cornea
by
Francisco J. Ávila, Óscar del Barco, María Concepción Marcellán and Laura Remón
Photonics 2024, 11(6), 524; https://doi.org/10.3390/photonics11060524 - 31 May 2024
Abstract
Corneal biomechanics is a hot topic in ophthalmology. The biomechanical properties (BMPs) of the cornea have important implications in the management and diagnosis of corneal diseases such as ectasia and keratoconus. In addition, the characterization of BMPs is crucial to model the predictability
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Corneal biomechanics is a hot topic in ophthalmology. The biomechanical properties (BMPs) of the cornea have important implications in the management and diagnosis of corneal diseases such as ectasia and keratoconus. In addition, the characterization of BMPs is crucial to model the predictability of a corneal surgery intervention, the outcomes of refractive surgery or the follow-up of corneal diseases. The biomechanical behavior of the cornea is governed by viscoelastic properties that allow, among other structural implications, the damping of excess intraocular pressure and the reduction of damage to the optic nerve. Currently, the most versatile and complete methods to measure corneal viscoelasticity are based on air-puff corneal applanation. However, these methods lack the ability to directly measure corneal viscosity. The aim of this work is to propose a new methodology based on the analysis of corneal air-puff measurements through the standard linear solid model (SLSM) to provide analytical expressions to separately calculate the elastic and time-dependent (corneal retardation time and viscosity) properties. The results show the mean values of elasticity (E), viscosity (Ƞ) and corneal retardation time (τ) in a sample of 200 young and healthy subjects. The influence of elasticity and viscosity on viscoelasticity, high-order corneal aberrations and optical transparency is investigated. Finally, the SLSM fed back from experimental E and Ƞ values is employed to compare the creep relaxation response between a normal, an ocular hypertension patient and an Ortho-K user. Corneal biomechanics is strongly affected by intraocular pressure (IOP); however, corneal hysteresis (CH) analysis is not enough to be employed as a risk factor of glaucoma progression. Low values of CH can be accompanied by high or low corneal elasticity and viscosity depending on the IOP threshold from which the time-dependent biomechanical properties trends are reversed.
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(This article belongs to the Special Issue Visual Optics)
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Open AccessArticle
Advanced Various Fault Detection Scheme for Long-Reach Mode Division Multiplexing Transmission
by
Feng Liu, Zicheng Huang and Tianle Gu
Photonics 2024, 11(6), 523; https://doi.org/10.3390/photonics11060523 - 30 May 2024
Abstract
This paper presents a few-mode fiber (FMF) various fault-detection method for long-reach mode division multiplexing (MDM) based on multi-mode transmission reflection analysis (MM-TRA). By injecting unmodulated continuous light into the FMF, and measuring and quantitatively analyzing the transmitted and reflected or Rayleigh backscattering
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This paper presents a few-mode fiber (FMF) various fault-detection method for long-reach mode division multiplexing (MDM) based on multi-mode transmission reflection analysis (MM-TRA). By injecting unmodulated continuous light into the FMF, and measuring and quantitatively analyzing the transmitted and reflected or Rayleigh backscattering power of different spatial modes, it is possible to accurately detect and locate reflective and non-reflective fault events. This paper discusses the localization accuracy of fault types such as FMF break, FMF link connector mismatch, and FMF bending. Theoretical analysis and simulation experimental results demonstrate that the proposed MM-TRA can provide an effective characterization of various faults and can achieve high fault localization accuracy. In addition, the influence of mode crosstalk of mode multiplexer/demultiplexer and mode coupling in FMF on the localization accuracy of various faults are considered. The results indicate that when using the combination of LP01 and LP21 modes, the localization errors for the FMF break, connector mismatch, and bending are 3.42 m, 1.97 m, and 3.29 m, respectively, demonstrating good fault localization performance.
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(This article belongs to the Section Lasers, Light Sources and Sensors)
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Open AccessReview
High-Resolution Retinal Imaging: Technology Overview and Applications
by
Mircea Mujat, R. Daniel Ferguson, Daniel X. Hammer, Ankit H. Patel and Nicusor Iftimia
Photonics 2024, 11(6), 522; https://doi.org/10.3390/photonics11060522 - 30 May 2024
Abstract
Adaptive optics (AO) has been used in many applications, including astronomy, microscopy, and medical imaging. In retinal imaging, AO provides real-time correction of the aberrations introduced by the cornea and the lens to facilitate diffraction-limited imaging of retinal microstructures. Most importantly, AO-based retinal
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Adaptive optics (AO) has been used in many applications, including astronomy, microscopy, and medical imaging. In retinal imaging, AO provides real-time correction of the aberrations introduced by the cornea and the lens to facilitate diffraction-limited imaging of retinal microstructures. Most importantly, AO-based retinal imagers provide cellular-level resolution and quantification of changes induced by retinal diseases and systemic diseases that manifest in the eye enabling disease diagnosis and monitoring of disease progression or the efficacy of treatments. In this paper, we present an overview of our team efforts over almost two decades to develop high-resolution retinal imagers suitable for clinical use. Several different types of imagers for human and small animal eye imaging are reviewed, and representative results from multiple studies using these instruments are shown. These examples demonstrate the extraordinary power of AO-based retinal imaging to reveal intricate details of morphological and functional characteristics of the retina and to help elucidate important aspects of vision and of the disruptions that affect delicate retinal tissue.
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(This article belongs to the Special Issue Adaptive Optics: Methods and Applications)
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Open AccessArticle
Period-Doubling Route to Chaos in Photorefractive Two-Wave Mixing
by
Subin Saju, Kenji Kinashi, Naoto Tsutsumi, Wataru Sakai and Boaz Jessie Jackin
Photonics 2024, 11(6), 521; https://doi.org/10.3390/photonics11060521 - 29 May 2024
Abstract
This paper investigates the possibilities of complex nonlinear dynamic signal generation using a simple photorefractive two-wave mixing system without any feedback using numerical simulations. The novel idea is to apply a sinusoidal electric field to the system inroder to extract nonlinear dynamic behavior.
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This paper investigates the possibilities of complex nonlinear dynamic signal generation using a simple photorefractive two-wave mixing system without any feedback using numerical simulations. The novel idea is to apply a sinusoidal electric field to the system inroder to extract nonlinear dynamic behavior. The mathematical model of the system was constructed using Kogelnick’s coupled wave equations and Kukhtarev’s material equation. The spatio-temporal evolution of the system was simulated in discrete steps numerically. The temporal evolution of the output light intensity exhibits period doubling, behavior which is a characteristic feature of complex nonlinear dynamic systems. A bifurcation diagram and Lyapunov exponentials confirm the presence of the period-doubling route to chaos in the system. The observed complex signal pattern varies uniformly with respect to the amplitude of the applied field, indicating a controllable nonlinear dynamic behavior. Such a system can be very useful in applications such as photonic reservoir computing, in-materio computing, photonic neuromorphic networks, complex signal detection, and time series prediction.
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(This article belongs to the Special Issue State-of-the-Art in Optical Materials)
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Open AccessCommunication
Four-Fold, Cross-Phase Modulation Driven UV Pulse Compression in a Thin Bulk Medium
by
Peter Susnjar, Alexander Demidovich, Gabor Kurdi, Paolo Cinquegrana, Ivaylo Nikolov, Paolo Sigalotti and Miltcho B. Danailov
Photonics 2024, 11(6), 520; https://doi.org/10.3390/photonics11060520 - 28 May 2024
Abstract
Generation of high energy few-fs pulses in the ultraviolet (UV) still represents challenges due to compression and phase control difficulties in this spectral range. Presented here is a pulse compression approach utilizing cross-phase modulation within a thin solid-state medium induced by a strong,
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Generation of high energy few-fs pulses in the ultraviolet (UV) still represents challenges due to compression and phase control difficulties in this spectral range. Presented here is a pulse compression approach utilizing cross-phase modulation within a thin solid-state medium induced by a strong, spatially and temporally controllable near-infrared (NIR) pulse acting on a weaker, 400 nm UV pulse. Through this method, four-fold compression is attained within a single fused silica plate, resulting in a 13 fs UV pulse with preserved beam quality. With some further technical adjustments, this method’s applicability could be extended to deep or even vacuum UV, where direct compression is difficult.
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(This article belongs to the Special Issue Recent Progress in Ultrafast Laser)
Open AccessArticle
Unraveling Electronic and Vibrational Coherences Following a Charge Transfer Process in a Photosystem II Reaction Center
by
Junhua Zhou, Xuanchao Zhang, Vandana Tiwari, Chao Mei, Ajay Jha, Pan-Pan Zhang and Hong-Guang Duan
Photonics 2024, 11(6), 519; https://doi.org/10.3390/photonics11060519 - 28 May 2024
Abstract
A reaction center is a unique biological system that performs the initial charge separation within a Photosystem II (PSII) multiunit enzyme, which eventually drives the catalytic water-splitting in plants and algae. The possible role of quantum coherences coinciding with the energy and charge
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A reaction center is a unique biological system that performs the initial charge separation within a Photosystem II (PSII) multiunit enzyme, which eventually drives the catalytic water-splitting in plants and algae. The possible role of quantum coherences coinciding with the energy and charge transfer processes in PSII reaction center is one of the active areas of research. Here, we study these quantum coherences by using a numerically exact method on an excitonic dimer model, including linear vibronic coupling and employing optimal parameters from experimental two-dimensional coherent spectroscopic measurements. This enables us to precisely capture the excitonic interaction between pigments and the dissipation of the energy from electronic and charge-transfer (CT) states to the protein environment. We employ the time nonlocal (TNL) quantum master equation to calculate the population dynamics, which yields numerically reliable results. The calculated results show that, due to the strong dissipation, the lifetime of electronic coherence is too short to have direct participation in the charge transfer processes. However, there are long-lived vibrational coherences present in the system at frequencies close to the excitionic energy gap. These are strongly coupled with the electronic coherences, which makes the detection of the electronic coherences with conventional techniques very challenging. Additionally, we unravel the strong excitonic interaction of radical pair ( and ) in the reaction center, which results in a long-lived electronic coherence of >100 fs, even at room temperature. Our work provide important physical insight to the charge separation process in PSII reaction center, which may be helpful for better understanding of photophysical processes in other natural and artificial light-harvesting systems.
Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
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