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
Wavelength-Tunable Chirped Pulse Amplification System (1720 nm–1800 nm) Based on Thulium-Doped Fiber
Photonics 2024, 11(5), 439; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050439 - 8 May 2024
Abstract
Chirped pulse amplification (CPA) has been a commonly used methodology to obtain powerful ultrashort laser pulses ever since its first demonstration. However, wavelength-tunable CPA systems are much less common. Wavelength-tunable ultrashort and intense laser pulses are desirable in various fields such as nonlinear
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Chirped pulse amplification (CPA) has been a commonly used methodology to obtain powerful ultrashort laser pulses ever since its first demonstration. However, wavelength-tunable CPA systems are much less common. Wavelength-tunable ultrashort and intense laser pulses are desirable in various fields such as nonlinear spectroscopy and optical parametric amplification. In this work, we report a 1720 nm–1800 nm tunable CPA system based on Tm-doped fiber. The tunable CPA system contains a seed laser, a pulse stretcher, two cascaded amplifiers and a pulse compressor. The dispersion-managed seed laser cavity emits wavelength-tunable laser pulses with pulse durations of several ps and spectral widths from 25 nm to 34 nm. After being stretched temporally to tens of ps, the laser pulses are then amplified in two-stage amplifiers and compressed in a Treacy-type compressor. At 1720 nm, the maximum average power of 126 mW is obtained with a pulse duration of 507 fs; at 1800 nm, the maximum average power of 264 mW is obtained with a pulse duration of 294 fs. The pulse repetition rates are around 22.7 MHz. We perform an analysis of the system design based on numerical simulations and go on to suggest further steps for improvement. To the best of our knowledge, this is the first demonstration of a tunable CPA system beyond 1.1 μm. Considering the specific wavelength range, this wavelength-tunable CPA system is highly desirable for biomedical imaging, sensing, and parametric amplifiers.
Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
Open AccessArticle
EUV Radiation in the Range of 10–20 nm from Liquid Spray Targets Containing O, Cl, Br and I Atoms under Pulsed Laser Excitation
by
Valerie E. Guseva, Andrey N. Nechay, Alexander A. Perekalov and Nicolay I. Chkhalo
Photonics 2024, 11(5), 438; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050438 - 8 May 2024
Abstract
The article describes the results of an investigation to determine the values of radiation intensities emitted by O-, Cl-, Br-, and I-containing liquid spray targets in absolute units in the wavelength range 10–20 nm when excited by pulsed laser radiation. The conversion coefficients
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The article describes the results of an investigation to determine the values of radiation intensities emitted by O-, Cl-, Br-, and I-containing liquid spray targets in absolute units in the wavelength range 10–20 nm when excited by pulsed laser radiation. The conversion coefficients of laser radiation into the EUV radiation are given for some wavelengths. The authors’ specially designed pulse extrusion liquid supply system was used to form the liquid spray targets. An Nd:YAG laser with λ = 1064 nm, τ = 8.4 ns, and Еpulse = 0.8 J was used to excite the targets. Spectral measurements were made using a grazing incidence grating spectrometer–monochromator. The absolute intensities of a number of emission lines were also measured using a Bragg spectrometer based on a Mo/Be multilayer X-ray mirror, calibrated by both sensitivity and wavelength. The high values of absolute intensities of the liquid targets in the extreme ultraviolet wavelength range were demonstrated.
Full article
(This article belongs to the Special Issue Advances and Applications of Solid State Lasers)
Open AccessArticle
Conversion and Active Control between BIC and Absorber in Terahertz Metasurface
by
Zhou Xi and Zhencheng Chen
Photonics 2024, 11(5), 437; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050437 - 8 May 2024
Abstract
A multifunctional switchable metamaterial device based on graphene, a gold layer, polyimide, vanadiµm dioxide (VO2), and the sapphire substrate is designed in this paper. The top layer consists of a gold wire, graphene, and two split-ring resonators with the same parameters.
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A multifunctional switchable metamaterial device based on graphene, a gold layer, polyimide, vanadiµm dioxide (VO2), and the sapphire substrate is designed in this paper. The top layer consists of a gold wire, graphene, and two split-ring resonators with the same parameters. By adjusting the Fermi level of graphene, the regulation of BIC and quasi-BIC is realized, and the conversion between BIC and absorber is realized by adjusting the conductivity of VO2. When the device is converted into a wave-absorbing device with single-band absorption characteristics, the Fermi level of graphene at this time is 0.001 eV, the absorption peak at 0.820 THz is higher than 99.5%, and when the Fermi level of regulated graphene is 1 eV, the absorption peak at 0.667 THz is also higher than 99.5%. The peak frequency of the device is 0.640 THz when it converts to quasi-BIC. To the best of our knowledge, this is the first time that the conversion and regulation of BIC and absorber have been achieved using these two phase change materials. Moreover, by adjusting the parameters of the metamaterial structure, the working efficiency and frequency of BIC and absorber can be dynamically adjusted. The electric field distribution and surface current of metamaterials are further studied, and the physical mechanism of effective absorption and BIC is discussed. These results show that the metamaterials proposed in this paper have many advantages, such as terahertz absorption, BIC, and active device control, and are of great significance for developing terahertz multifunctional devices.
Full article
(This article belongs to the Section Optoelectronics and Optical Materials)
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Open AccessArticle
The Optimization of Microwave Field Characteristics for ODMR Measurement of Nitrogen-Vacancy Centers in Diamond
by
Zhenxian Fan, Li Xing, Feixiang Wu, Xiaojuan Feng and Jintao Zhang
Photonics 2024, 11(5), 436; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050436 - 8 May 2024
Abstract
A typical solid-state quantum sensor can be developed based on negatively charged nitrogen-vacancy (NV−) centers in diamond. The electron spin state of NV− can be controlled and read at room temperature. Through optical detection magnetic resonance (ODMR) technology, temperature measurement
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A typical solid-state quantum sensor can be developed based on negatively charged nitrogen-vacancy (NV−) centers in diamond. The electron spin state of NV− can be controlled and read at room temperature. Through optical detection magnetic resonance (ODMR) technology, temperature measurement can be achieved at the nanoscale. The key to ODMR technology is to apply microwave resonance to manipulate the electron spin state of the NV−. Therefore, the microwave field characteristics formed near the NV− have a crucial impact on the sensitivity of ODMR measurement. This article mainly focuses on the temperature situation in cellular applications and simulates the influence of structural parameters of double open loop resonant (DOLR) microwave antennas and broadband large-area (BLA) microwave antennas on the microwave field’s resonance frequency, quality factor Q, magnetic field strength, uniformity, etc. The parameters are optimized to have sufficient bandwidth, high signal-to-noise ratio, low power loss, and high magnetic field strength in the temperature range of 36 °C to 42.5 °C. Finally, the ODMR spectra are used for effect comparison, and the signal-to-noise ratio and Q values of the ODMR spectra are compared when using different antennas. We have provided an optimization method for the design of microwave antennas and it is concluded that the DOLR microwave antenna is more suitable for living cell temperature measurement in the future.
Full article
(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)
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Open AccessArticle
Discriminating Glioblastoma from Normal Brain Tissue In Vivo Using Optical Coherence Tomography and Angiography: A Texture and Microvascular Analysis Approach
by
Trung Nguyễn-Hoàng, Tai-Ang Wang, Chia-Heng Wu and Meng-Tsan Tsai
Photonics 2024, 11(5), 435; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050435 - 8 May 2024
Abstract
Brain tumors arise from abnormal cell growth in the brain. Glioblastoma, the most common and aggressive type, poses significant challenges for identification during surgery. The primary goal of this study is to identify and differentiate normal brain tissue from glioblastoma tissue using optical
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Brain tumors arise from abnormal cell growth in the brain. Glioblastoma, the most common and aggressive type, poses significant challenges for identification during surgery. The primary goal of this study is to identify and differentiate normal brain tissue from glioblastoma tissue using optical coherence tomography (OCT) and OCT angiography (OCTA). These techniques offer a non-invasive way to analyze the morphological and microvascular alternations associated with glioblastoma in an animal model. To monitor the changes in morphology and vascular distribution of brain tissue as glioblastoma tumors grow, time-series OCT and OCTA results were collected for comparison. Texture analysis of OCT images was proposed using the gray-level co-occurrence matrix (GLCM), from which homogeneity and variance were calculated as discriminative parameters. Additionally, OCTA was used to assess microvascular characteristics, including vessel diameter, density, and fractal dimension. The findings demonstrate that the proposed methods can effectively distinguish between normal and cancerous brain tissue in vivo.
Full article
(This article belongs to the Special Issue Photonics: 10th Anniversary)
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Open AccessArticle
Rare-Earth-Ion (RE3+)-Doped Aluminum and Lanthanum Borates for Mobile-Phone-Interrogated Luminescent Markers
by
Katya Hristova, Irena P. Kostova, Tinko A. Eftimov, Daniel Brabant and Samia Fouzar
Photonics 2024, 11(5), 434; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050434 - 6 May 2024
Abstract
In this paper, we present the synthesis and luminescent spectra of rare-earth (RE)-doped aluminum and lanthanum borates intended to serve as narrow excitation–emission band fluorescent markers. We perform a detailed 3D excitation–emission matrix (EEM) analysis of their spectra, compare the measurements from both
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In this paper, we present the synthesis and luminescent spectra of rare-earth (RE)-doped aluminum and lanthanum borates intended to serve as narrow excitation–emission band fluorescent markers. We perform a detailed 3D excitation–emission matrix (EEM) analysis of their spectra, compare the measurements from both standard and mobile phone spectrometers, and outline the basic differences and advantages of each method. While smartphones have a different and non-uniform spectral response compared to standard spectrometers, it is shown that they offer a number of advantages such as contactless interrogation, efficient suppression of the UV excitation light, and simultaneous spectral analysis of spatially arranged arrays of fluorescent markers. The basic emission peaks have been observed and their corresponding electronic transitions identified. The obtained results show that the rare-earth-doped La and Al borates feature excitation–emission bandwidths as low 15 nm/12 nm, which makes them particularly appropriate for use as luminescent markers with UV LED excitation and smartphone interrogation.
Full article
(This article belongs to the Topic Optical and Optoelectronic Properties of Materials and Their Applications)
Open AccessArticle
Dead Zone Fault Detection Optimization Method for Few-Mode Fiber Links Based on Unexcited Coupled Higher-Order Modes
by
Feng Liu, Tianle Gu and Zicheng Huang
Photonics 2024, 11(5), 433; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050433 - 6 May 2024
Abstract
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The traditional single-mode fiber (SMF) optical time domain reflectometer (OTDR) may not be able to accurately detect and locate fault events in the dead zone of few-mode fiber (FMF) links. This paper introduces the concept of higher-order spatial mode detection dimensions unique to
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The traditional single-mode fiber (SMF) optical time domain reflectometer (OTDR) may not be able to accurately detect and locate fault events in the dead zone of few-mode fiber (FMF) links. This paper introduces the concept of higher-order spatial mode detection dimensions unique to FMF, combined with the spatial mode coupling characteristics between modes. The Fresnel reflection from the end face of the fiber, the interior of the circulator, and the connector only occurs in the spatial mode of the injected optical pulse. The Rayleigh backscattering, which reflects the fault distribution characteristics of FMF links, can be detected by non-excited higher-order spatial modes. The proposed method can completely overcome the traditional OTDR dead zone. In this paper, the six-mode fiber is taken as an example for experimental verification. The detection optical pulse is injected into the fundamental mode LP01, and the Rayleigh backscattering of LP11a, LP11b, LP21a, LP21b, and LP02 higher-order spatial mode are collected and analyzed to accurately detect and locate the fusion splice fault event at 100 m and 500 m in the dead zone.
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Open AccessArticle
Mid-Infrared 2.79 μm Band Er, Cr: Y3Sc2Ga3O12 Laser Transmission Anti-Bending Low-Loss Anti-Resonant Hollow-Core Fiber
by
Lei Huang, Peng Wang, Yinze Wang, Tingqing Cheng, Li Wang and Haihe Jiang
Photonics 2024, 11(5), 432; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050432 - 5 May 2024
Abstract
A large core size and bending resistance are very important properties of mid-infrared energy transfer fibers, but large core sizes usually lead to the deterioration of bending properties. A negative-curvature nested node-free anti-resonant hollow-core fiber (AR-HCF) based on quartz is proposed. It was
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A large core size and bending resistance are very important properties of mid-infrared energy transfer fibers, but large core sizes usually lead to the deterioration of bending properties. A negative-curvature nested node-free anti-resonant hollow-core fiber (AR-HCF) based on quartz is proposed. It was made by adding a nested layer to a previous AR-HCF design to provide an additional anti-resonance region while keeping the gap between adjacent tubes strictly correlated with the core diameter to produce a node-free structure. These features improve the fiber’s bending resistance while achieving a larger core diameter. The simulation results show that the radial air–glass anti-resonant layer is increased by the introduction of the nested anti-resonant tube, and the weak interference overlap between the fiber core and the cladding mode is reduced, so the fiber core’s limiting loss and sensitivity to bending are effectively reduced. When the capillary wall thickness t of the fiber is 0.71 μm, the core diameter D is 70 μm, the ratio of the inner diameter of the cladding capillary to the core diameter d/D is 0.62, the diameter of the nested tube is d0 = 29 μm, the fiber has a lower limiting loss at the wavelength of 2.79 μm, and the limiting loss is 3.28 × 10−4 dB/m. At the same time, the optimized structure also has good bending resistance. When the bending radius is 30 mm, the bending loss is only 4.72 × 10−2 dB/m. An anti-bending low-loss micro-structure hollow fiber with a bending radius of less than 30 mm was successfully achieved in the 2.79 μm band. An anti-bending low-loss anti-resonant hollow-core fiber with this structure constitutes a reliable choice for the light guiding system of a 2.79 μm band Er, Cr: YSGG laser therapy instrument.
Full article
(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)
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Open AccessArticle
Global Receptive Field Designed Complex-Valued Convolutional Neural Network Equalizer for Optical Fiber Communications
by
Lu Han, Yongjun Wang, Haifeng Yang, Yang Zhao and Chao Li
Photonics 2024, 11(5), 431; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050431 - 5 May 2024
Abstract
In this paper, an improved complex-valued convolutional neural network (CvCNN) structure to be placed at the received side is proposed for nonlinearity compensation in a coherent optical system. This complex-valued global convolutional kernel-assisted convolutional neural network equalizer (CvGNN) has been verified in terms
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In this paper, an improved complex-valued convolutional neural network (CvCNN) structure to be placed at the received side is proposed for nonlinearity compensation in a coherent optical system. This complex-valued global convolutional kernel-assisted convolutional neural network equalizer (CvGNN) has been verified in terms of Q-factor performance and complexity compared to seven other related nonlinear equalizers based on both the 64 QAM experimental platform and the QPSK numerical platform. The global convolution operation of the proposed CvGNN is more suitable for the calculation process of perturbation coefficients, and the global receptive field can also be more effective at extracting effective information from perturbation feature maps. The introduction of CvCNN can directly focus on the complex-valued perturbation feature maps themselves without separately processing the real and imaginary parts, which is more in line with the waveform-dependent physical characteristics of optical signals. Based on the experimental platform, compared with the real-valued neural network with small convolutional kernel (RvCNNC), the proposed CvGNNC improves the Q-factor by ∼2.95 dB at the optimal transmission power, while reducing the time complexity by ∼44.7%.
Full article
(This article belongs to the Section Optical Communication and Network)
Open AccessArticle
Polarization Strips in the Focus of a Generalized Poincaré Beam
by
Victor V. Kotlyar, Alexey A. Kovalev, Alexey M. Telegin and Elena Sergeevna Kozlova
Photonics 2024, 11(5), 430; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050430 - 4 May 2024
Abstract
We analyze the tight focusing of a generalized Poincaré beam using a Richards–Wolf formalism. Conventional Poincaré beams are superpositions of two Laguerre–Gaussian beams with orthogonal polarization, while the generalized Poincaré beams are composed of two arbitrary optical vortices with rotationally symmetric amplitudes. Analytical
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We analyze the tight focusing of a generalized Poincaré beam using a Richards–Wolf formalism. Conventional Poincaré beams are superpositions of two Laguerre–Gaussian beams with orthogonal polarization, while the generalized Poincaré beams are composed of two arbitrary optical vortices with rotationally symmetric amplitudes. Analytical relationships for projections of the electric field in the focal plane are derived. Using the superposition of a right-handed circularly polarized plane wave and an optical vortex with a topological charge of −1 as an example, relationships for the intensity distribution and the longitudinal projection of the spin angular momentum vector are deduced. It is theoretically and numerically shown that the original beam has a topological charge of –1/2 and a C-point of circular polarization, and it is generated at the focal plane center, producing an on-axis C-line with a singularity index of –1/2 (a star). Furthermore, when making a full circle of some radius around the optical axis, the major axis vector of polarization ellipse is theoretically and numerically shown to form a one-sided polarization (Möbius) strip of order −3/2, which has three half-twists and a single ‘patching’ in which two oppositely directed vectors of the major axis of polarization ellipse occur close to each other.
Full article
(This article belongs to the Special Issue Recent Advances in Diffractive Optics)
Open AccessArticle
Efficient Pipeline Conflict Resolution for Layered QC-LDPC Decoders in OFDM-PON
by
Zhijie Wang, Zhengjun Xu, Kun Chen, Yuanzhe Qu, Xiaoqun Liu, Yingchun Li and Junjie Zhang
Photonics 2024, 11(5), 429; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050429 - 4 May 2024
Abstract
The high standard of communication quality in optical access networks makes forward error correction (FEC) schemes, such as LDPC, an integral part of the system. However, pipeline conflict arising from data dependencies is a common issue encountered in the hardware implementation of layered
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The high standard of communication quality in optical access networks makes forward error correction (FEC) schemes, such as LDPC, an integral part of the system. However, pipeline conflict arising from data dependencies is a common issue encountered in the hardware implementation of layered QC-LDPC decoders. This paper proposes an efficient layered decoding architecture to reduce pipeline conflicts without introducing stall cycles. It can solve some of the pipeline conflicts by flexibly reordering the processing order of inter-layer and intra-layer submatrices offline. In addition, the patch method, based on variable-to-check messages, allows for the delayed use of gains between layer iterations, which can further minimize the performance loss caused by the remaining pipeline conflicts. The experimental results on the LDPC code of the IEEE802.16 standard in the OFDM-PON system demonstrate that the proposed architecture has sensitivity improvements of 0.125 dBm and 0.375 dBm, respectively, compared with our previous work and the method described in the other work. The optimized architecture improves the reliability of the decoder and can also make a contribution to efficient PON systems.
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(This article belongs to the Section Optical Communication and Network)
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Open AccessArticle
Tightly Trapped Atom Interferometer inside a Hollow-Core Fiber
by
Yitong Song, Wei Li, Xiaobin Xu, Rui Han, Chengchun Gao, Cheng Dai and Ningfang Song
Photonics 2024, 11(5), 428; https://doi.org/10.3390/photonics11050428 - 3 May 2024
Abstract
We demonstrate a fiber-guided atom interferometer in a far-off-resonant trap (FORT) of 100 μK. The differential light shift (DLS) introduced by the FORT leads to the inhomogeneous dephasing of the tightly trapped atoms inside a hollow-core fiber. The DLS-induced dephasing is greatly suppressed
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We demonstrate a fiber-guided atom interferometer in a far-off-resonant trap (FORT) of 100 μK. The differential light shift (DLS) introduced by the FORT leads to the inhomogeneous dephasing of the tightly trapped atoms inside a hollow-core fiber. The DLS-induced dephasing is greatly suppressed in Doppler-insensitive interferometry. The spin coherence time is extended to 13.4 ms by optimizing the coupling of the trapping laser beam into a quasi-single-mode hollow-core anti-resonant fiber. The Doppler-sensitive interferometry shows a much shorter coherence time, indicating that the main limits to our fiber-guided atom interferometer are the wide axial velocity distribution and the irregular modes of the Raman laser beams inside the fiber. This work paves the way for portable and miniaturized quantum devices, which have advantages for inertial sensing at arbitrary orientations and in dynamic environments.
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(This article belongs to the Special Issue The Integration of Quantum Communication and Quantum Sensors)
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Open AccessArticle
Improved Optics for Super-Resolution Time-Lapse Observations of Biological Phenomenon Using Speckle Interferometry
by
Yasuhiko Arai
Photonics 2024, 11(5), 427; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050427 - 3 May 2024
Abstract
This study proposes a new optical system with the potential for time-lapse observation of living cellular tissue beyond the diffraction limit through speckle interferometry to facilitate biological research. The spatial resolution of this optical system was investigated and improved upon. This study also
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This study proposes a new optical system with the potential for time-lapse observation of living cellular tissue beyond the diffraction limit through speckle interferometry to facilitate biological research. The spatial resolution of this optical system was investigated and improved upon. This study also experimentally verified a finding from an earlier simulation study that the new super-resolution technology could be realised by analysing the phase distribution related to the shape of the measured object, preserved in the light reflected from the object. Additionally, a method was presented to confirm the positions of microstructures, based on the extracted characteristics of the structure.
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(This article belongs to the Special Issue Coherence Properties of Light: From Theory to Applications)
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An Empirical Approach to Rerouting Visible Light Pathways Using an Adjustable-Angle Mirror to Sustain Communication between Vehicles on Curvy Roads
by
Ahmet Deniz, Burak Aydın and Heba Yuksel
Photonics 2024, 11(5), 426; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050426 - 3 May 2024
Abstract
In this paper, a novel method is demonstrated to sustain vehicle-to-vehicle (V2V) communication on curvy roads via the arrangement of the lateral position of a self-angle-adjustable mirror–reflective road sign (SAAMRS) and light-direction-sensing wide-angle complementary photodiodes (CPDs). Visible light communication (VLC) between vehicles attracts
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In this paper, a novel method is demonstrated to sustain vehicle-to-vehicle (V2V) communication on curvy roads via the arrangement of the lateral position of a self-angle-adjustable mirror–reflective road sign (SAAMRS) and light-direction-sensing wide-angle complementary photodiodes (CPDs). Visible light communication (VLC) between vehicles attracts attention as a complementary technology to radio-frequency-based (RF-based) communication technologies due to its wide, license-free spectrum and immunity to interferences. However, V2V VLC may be interrupted on curvy roads due to the limited field of view (FOV) of the receiver or the line of sight (LOS) being interrupted. To solve this problem, an experiment was developed using an SAAMRS along with wide-angle light-direction-sensing CPDs that used a precise peak detection (PPD) method to sustain communication between vehicles in dynamic environments by rerouting the incident light with the highest signal intensity level to the receiver vehicle on curvy roads. We also used real images of curvy roads simulated as polynomials to calculate the necessary rotation angles for the SAAMRS and regions where communication exist. Our experimental results overlapped almost completely with our simulations, with small errors of approximately 4.8% and 4.4% for the SAAMRS angle and communication region, respectively.
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(This article belongs to the Special Issue Visible Light Communications)
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Open AccessArticle
Polarization Diffraction Gratings in PAZO Polymer Thin Films Recorded with Digital Polarization Holography: Polarization Properties and Surface Relief Formation
by
Nataliya Berberova-Buhova, Lian Nedelchev, Georgi Mateev, Ludmila Nikolova, Elena Stoykova, Branimir Ivanov, Velichka Strijkova, Keehoon Hong and Dimana Nazarova
Photonics 2024, 11(5), 425; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050425 - 3 May 2024
Abstract
In this work, we study the polarization properties of diffraction gratings recorded in thin films of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt]) using digital polarization holography. Using two quarter-wave plates, the phase retardation of each pixel of the SLM is converted into
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In this work, we study the polarization properties of diffraction gratings recorded in thin films of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt]) using digital polarization holography. Using two quarter-wave plates, the phase retardation of each pixel of the SLM is converted into the azimuth rotation of linearly polarized light. When recording from the azopolymer side of the sample, significant surface relief amplitude is observed with atomic force microscopy. In contrast, recording from the substrate side of the sample allows the reduction of the surface relief modulation and the obtaining of polarization gratings with characteristics close to an ideal grating, recorded with two orthogonal circular polarizations. This can be achieved even with a four-pixel period of grating, as demonstrated by our results.
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(This article belongs to the Special Issue Technologies and Applications of Digital Holography)
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Deep Learning-Enhanced Inverse Modeling of Terahertz Metasurface Based on a Convolutional Neural Network Technique
by
Muzhi Gao, Dawei Jiang, Gaoyang Zhu and Bin Wang
Photonics 2024, 11(5), 424; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050424 - 3 May 2024
Abstract
The traditional design method for terahertz metasurface biosensors is cumbersome and time-consuming, requires expertise, and often leads to significant discrepancies between expected and actual values. This paper presents a novel approach for the fast, efficient, and convenient inverse design of THz metasurface sensors,
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The traditional design method for terahertz metasurface biosensors is cumbersome and time-consuming, requires expertise, and often leads to significant discrepancies between expected and actual values. This paper presents a novel approach for the fast, efficient, and convenient inverse design of THz metasurface sensors, leveraging convolutional neural network techniques based on deep learning. During the model training process, the magnitude data of the scattering parameters collected from the numerical simulation of the THz metasurface served as features, paired with corresponding surface structure matrices as labels to form the training dataset. During the validation process, the thoroughly trained model precisely predicted the expected surface structure matrix of a THz metasurface. The results demonstrate that the proposed algorithm realizes time-saving, high-efficiency, and high-precision inversion methods without complicated data preprocessing and additional optimization algorithms. Therefore, deep learning algorithms offer a novel approach for swiftly designing and optimizing THz metasurface sensors in biomedical detection, bypassing the complex and specialized design process of electromagnetic devices, and promising extensive prospects for their application in the biomedical field.
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(This article belongs to the Special Issue Fiber Optic Sensors: Science and Applications)
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Intermodal Fiber Interferometer with Spectral Interrogation and Fourier Analysis of Output Signals for Sensor Application
by
Aleksandr Petrov, Andrey Golovchenko, Mikhail Bisyarin, Nikolai Ushakov and Oleg Kotov
Photonics 2024, 11(5), 423; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050423 - 2 May 2024
Abstract
Interferometric fiber-optic sensors provide very high measurement accuracy and come with many other benefits. As such, the study of signal processing techniques for fiber-optic interferometers in order to extract information about external perturbation is an important area of research. In this work, the
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Interferometric fiber-optic sensors provide very high measurement accuracy and come with many other benefits. As such, the study of signal processing techniques for fiber-optic interferometers in order to extract information about external perturbation is an important area of research. In this work, the method of Fourier analysis was applied to extract information from the output signals of an intermodal fiber interferometer with spectral interrogation. It is shown that the external perturbation can be measured by obtaining the phase spectrum of the spectral transfer function of an intermodal fiber interferometer and determining the phase difference of a certain pair of mode groups. A mathematical model of this approach was developed, taking into account the parameters of the laser and the optical fiber, the number of excited mode groups, and the parameters of external perturbation. The theoretically considered method of Fourier analysis was experimentally verified, and it was proved to provide a linear response to external perturbation in a wide dynamic range.
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(This article belongs to the Special Issue Fiber Optic Sensors: Science and Applications)
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Open AccessArticle
High-Precision Semiconductor Substrate Thickness Gauge Based on Spectral-Domain Interferometry
by
Shuncong Zhong, Renyu He, Yaosen Deng, Jiewen Lin and Qiukun Zhang
Photonics 2024, 11(5), 422; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050422 - 1 May 2024
Abstract
The flatness of semiconductor substrates is an important parameter for evaluating the surface quality of semiconductor substrates. However, existing technology cannot simultaneously achieve high measurement efficiency, large-range thickness measurement, and nanometer-level measurement accuracy in the thickness measurement of semiconductor substrates. To solve the
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The flatness of semiconductor substrates is an important parameter for evaluating the surface quality of semiconductor substrates. However, existing technology cannot simultaneously achieve high measurement efficiency, large-range thickness measurement, and nanometer-level measurement accuracy in the thickness measurement of semiconductor substrates. To solve the problems, we propose to apply the method that combines spectral-domain optical coherence tomography (SD-OCT) with the Hanning-windowed energy centrobaric method (HnWECM) to measure the thickness of semiconductor substrates. The method can be employed in the full-chip thickness measurement of a sapphire substrate, which has a millimeter measuring range, nanometer-level precision, and a sampling rate that can reach up to 80 kHz. In this contribution, we measured the full-chip thickness map of a sapphire substrate by using this method and analyzed the machining characteristics. The measurement results of a high-precision mechanical thickness gauge, which is widely used for thickness measurement in the wafer fabrication process, were compared with the proposed method. The difference between these two methods is 0.373%, which explains the accuracy of the applied method to some extent. The results of 10 sets of repeatability experiments on 250 measurement points show that the maximum relative standard deviation (RSD) at this point is 0.0061%, and the maximum fluctuation is 71.0 nm. The above experimental results prove that this method can achieve the high-precision thickness measurement of the sapphire substrate and is of great significance for improving the surface quality detection level of semiconductor substrates.
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(This article belongs to the Topic Advance and Applications of Fiber Optic Measurement: 2nd Edition)
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Open AccessArticle
Group Control of Photo-Responsive Colloidal Motors with a Structured Light Field
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Dianyang Li, Huan Wei, Hui Fang and Yongxiang Gao
Photonics 2024, 11(5), 421; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050421 - 1 May 2024
Abstract
Using structured light to drive colloidal motors, due to its advantages of remote manipulation, energy tunability, programmability, and the controllability of spatiotemporal distribution, has been attracting much attention in the fields of targeted drug delivery, environmental control, chemical agent detection, and smart device
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Using structured light to drive colloidal motors, due to its advantages of remote manipulation, energy tunability, programmability, and the controllability of spatiotemporal distribution, has been attracting much attention in the fields of targeted drug delivery, environmental control, chemical agent detection, and smart device design. Here, we focus on studying the group control of colloidal motors made from a photo-responsive organic polymer molecule NO-COP (N,O-Covalent organic polymer). These colloidal motors mainly respond to light intensity patterns. Considering its merits of fast refreshing speed, good programmability, and high-power threshold, we chose a digital micromirror device (DMD) to modulate the structured light field shining on the sample. It was found that under ultraviolet or green light modulation, such colloidal motors exhibit various group behaviors including group spreading, group patterning, and group migration. A qualitative interpretation is also provided for these observations.
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(This article belongs to the Special Issue Emerging Topics in Structured Light)
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Functional Optical Coherence Tomography of Rat Cortical Neurovascular Activation during Monopulse Electrical Stimulation with the Microelectrode Array
by
Lin Yao, Jin Huang, Taixiang Liu, Han Gu, Changpeng Li, Ke Yang, Hongwei Yan, Lin Huang, Xiaodong Jiang, Chengcheng Wang and Qihua Zhu
Photonics 2024, 11(5), 420; https://0-doi-org.brum.beds.ac.uk/10.3390/photonics11050420 - 30 Apr 2024
Abstract
This paper presents a study to evoke rat cortical functional activities, including hemodynamic and neural tissue signal changes, by monopulse electrical stimulation with a microelectrode array using functional optical coherence tomography (fOCT). Based on the principal component analysis and fuzzy clustering method (PCA-FCM),
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This paper presents a study to evoke rat cortical functional activities, including hemodynamic and neural tissue signal changes, by monopulse electrical stimulation with a microelectrode array using functional optical coherence tomography (fOCT). Based on the principal component analysis and fuzzy clustering method (PCA-FCM), the hemodynamic response of different size blood vessels in rat cortex are analyzed, showing that the hemodynamic response of the superficial large blood vessels is more concentrated. In the regions of neural tissue where blood vessels are removed, positive significant pixels (the intensity of the pixel for five consecutive frames is greater than the average value plus triple standard deviation) and negative significant pixels (the intensity of the pixel for five consecutive frames is less than the average value minus triple standard deviation) exist, and the averaged intensity signal responds rapidly with an onset time of ~20.8 ms. Furthermore, the hemodynamic response was delayed by ~3.5 s from the neural tissue response. fOCT can provide a label-free, large-scale and depth-resolved map of cortical neurovascular activation, which is a promising technology to monitor cortical small-scale neurovascular activities.
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(This article belongs to the Section Biophotonics and Biomedical Optics)
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