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
Double-Cycle Alternating-Flow Diode Pumped Potassium Vapor Laser
Photonics 2024, 11(5), 391; https://doi.org/10.3390/photonics11050391 - 23 Apr 2024
Abstract
A novel double-cycle alternating-flow diode-pumped potassium vapor laser is proposed, theoretically modeled and simulated. The results show that the optical-to-optical efficiency of the laser increases with increasing gas flow rates, although at high flow rates the rate of increase in efficiency decreases. The
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A novel double-cycle alternating-flow diode-pumped potassium vapor laser is proposed, theoretically modeled and simulated. The results show that the optical-to-optical efficiency of the laser increases with increasing gas flow rates, although at high flow rates the rate of increase in efficiency decreases. The optical-to-optical efficiency reaches 74.8% at a pump power density of 30 kW/cm2 and a gas flow rate of 50 m/s. The optical-to-optical efficiency of the laser is greater with a narrow linewidth pump and high buffer gas pressure. The optical-to-optical efficiency of a flow gas cell is higher than that of a static gas cell. There is an optimal gas cell length that provides the highest optical-to-optical efficiency. At higher pump power densities, higher flow rates are required to obtain higher optical-to-optical efficiencies.
Full article
(This article belongs to the Special Issue High-Power Infrared Laser Systems: Design, Characterization, and Applications)
Open AccessArticle
Modulation Format Identification Based on Multi-Dimensional Amplitude Features for Elastic Optical Networks
by
Ming Hao, Wei He, Xuedong Jiang, Shuai Liang, Wei Jin, Lin Chen and Jianming Tang
Photonics 2024, 11(5), 390; https://doi.org/10.3390/photonics11050390 - 23 Apr 2024
Abstract
A modulation format identification (MFI) scheme based on multi-dimensional amplitude features is proposed for elastic optical networks. According to the multi-dimensional amplitude features, incoming polarization division multiplexed (PDM) signals can be identified as QPSK, 8QAM, 16QAM, 32QAM, 64QAM and 128QAM signals using the
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A modulation format identification (MFI) scheme based on multi-dimensional amplitude features is proposed for elastic optical networks. According to the multi-dimensional amplitude features, incoming polarization division multiplexed (PDM) signals can be identified as QPSK, 8QAM, 16QAM, 32QAM, 64QAM and 128QAM signals using the k-nearest neighbors (KNNs) algorithm in the digital coherent receivers. The proposed scheme does not require any prior training or optical signal-to-noise ratio (OSNR) information. The performance of the proposed MFI scheme is verified based on numerical simulations with 28GBaud PDM-QPSK/-8QAM/-16QAM/-32QAM/-64QAM/-128QAM signals. The results show that the proposed scheme can achieve 100% of the correct MFI rate for all six modulation formats when the OSNR values are greater than their thresholds corresponding to the 20% forward error correction (FEC) related to a BER of 2.4 × 10−2. Meanwhile, the effects of residual chromatic dispersion, polarization mode dispersion and fiber nonlinearities on the proposed scheme are also explored. Finally, the computational complexity of the proposed scheme is analyzed, which is compared with relevant MFI schemes. The work indicates that the proposed technique could be regarded as a good candidate for identifying modulation formats up to 128QAM.
Full article
(This article belongs to the Special Issue Optical Performance Monitoring)
Open AccessArticle
Amplified Nonreciprocal Reflection in a Uniform Atomic Medium with the Help of Spontaneous Emissions
by
Xinyu Lin, Xinfu Zheng, Yue Geng, Guanrong Li, Qiongyi Xu, Jinhui Wu, Dong Yan and Hong Yang
Photonics 2024, 11(4), 389; https://doi.org/10.3390/photonics11040389 - 22 Apr 2024
Abstract
It is important to elaborate on versatile strategies for achieving the perfect nonreciprocal reflection amplification, which is the key technology of high-quality nonreciprocal photonic devices. In this work, we ingeniously design a coherent four-level N-type atomic system to harness the nonreciprocal light
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It is important to elaborate on versatile strategies for achieving the perfect nonreciprocal reflection amplification, which is the key technology of high-quality nonreciprocal photonic devices. In this work, we ingeniously design a coherent four-level N-type atomic system to harness the nonreciprocal light amplification, in which the uniform distribution of atoms is driven by two strong coupling fields and a weak probe field. In our regime, the strength of the two control fields is designed with linear variation along the x direction to destroy the spatial symmetry of the probe susceptibility, leading to the nonreciprocity of the reflection. In particular, the closed-loop transitions to amplify the probe field are due to the combined effect of the control fields and spontaneous emissions. The numerical simulation indicates that the perfect nonreciprocal reflection amplification can be realized and modulated by the appropriate settings of the control fields and the detuning, . Our results will open a new route toward harnessing nonreciprocity, which can provide more convenience and possibilities in experimental realization.
Full article
(This article belongs to the Special Issue Optical Quantum System)
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Open AccessArticle
HoloDiffusion: Sparse Digital Holographic Reconstruction via Diffusion Modeling
by
Liu Zhang, Songyang Gao, Minghao Tong, Yicheng Huang, Zibang Zhang, Wenbo Wan and Qiegen Liu
Photonics 2024, 11(4), 388; https://doi.org/10.3390/photonics11040388 - 21 Apr 2024
Abstract
In digital holography, reconstructed image quality can be primarily limited due to the inability of a single small aperture sensor to cover the entire field of a hologram. The use of multi-sensor arrays in synthetic aperture digital holographic imaging technology contributes to overcoming
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In digital holography, reconstructed image quality can be primarily limited due to the inability of a single small aperture sensor to cover the entire field of a hologram. The use of multi-sensor arrays in synthetic aperture digital holographic imaging technology contributes to overcoming the limitations of sensor coverage by expanding the area for detection. However, imaging accuracy is affected by the gap size between sensors and the resolution of sensors, especially when dealing with a limited number of sensors. An image reconstruction method is proposed that combines physical constraint characteristics of the imaging object with a score-based diffusion model, aiming to enhance the imaging accuracy of digital holography technology with extremely sparse sensor arrays. Prior information of the sample is learned by the neural network in the diffusion model to obtain a score function, which alternately constrains the iterative reconstruction process with the underlying physical model. The results demonstrate that the structural similarity and peak signal-to-noise ratio of the reconstructed images using this method are higher than the traditional method, along with a strong generalization ability.
Full article
(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)
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Open AccessArticle
Similariton-like Pulse Evolution in an Er-Doped Fiber Laser with Hybrid Mode Locking
by
Aleksander Y. Fedorenko, Almikdad Ismaeel, Ilya O. Orekhov, Dmitriy A. Dvoretskiy, Stanislav G. Sazonkin, Lev K. Denisov and Valeriy E. Karasik
Photonics 2024, 11(4), 387; https://doi.org/10.3390/photonics11040387 - 21 Apr 2024
Abstract
An Er-doped all-fiber ultrashort pulse laser with positive total net-cavity group-velocity dispersion is demonstrated based on a hybrid mode-locking mechanism ensured by single-walled carbon–boron–nitrogen nanotubes with coaction of the nonlinear polarization evolution effect. The generation regime with a similariton-like spectrum is obtained. The
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An Er-doped all-fiber ultrashort pulse laser with positive total net-cavity group-velocity dispersion is demonstrated based on a hybrid mode-locking mechanism ensured by single-walled carbon–boron–nitrogen nanotubes with coaction of the nonlinear polarization evolution effect. The generation regime with a similariton-like spectrum is obtained. The spectrum width is ~31.5 nm, and the minimal pulse duration is ~294 fs at full width at half maximum. The average output power is ~3.2 mW, corresponding to 0.376 nJ pulse energy and 1.25 kW peak power. The fundamental pulse repetition rate is ~8.5 MHz, with a signal-to-noise ratio of 60 dB. The standard deviation of average output optical power stability, measured for 12 h, is about ~1% RMS, and the maximum level of relative intensity noise (RIN) does not exceed <−120 dBc/Hz in the 30 Hz–1 MHz frequency range. To prove the similariton-like regime generation, we also studied numerically and experimentally the pulse evolution during propagation through a laser resonator and output single-mode fiber with anomalous dispersion.
Full article
(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)
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Open AccessArticle
All-Solid-State Post-Compression of Low-Energy Pulses at High Repetition Rate
by
Vaida Marčiulionytė, Jonas Banys, Julius Vengelis, Gintaras Tamošauskas and Audrius Dubietis
Photonics 2024, 11(4), 386; https://doi.org/10.3390/photonics11040386 - 19 Apr 2024
Abstract
We demonstrate a proof of principle of a simple all-solid-state post-compression setup for low-energy, high-repetition-rate laser pulses, where spectral broadening was performed using a combination of highly nonlinear bulk materials in a simple single-pass geometry. The 75 fs, 210 nJ pulses from an
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We demonstrate a proof of principle of a simple all-solid-state post-compression setup for low-energy, high-repetition-rate laser pulses, where spectral broadening was performed using a combination of highly nonlinear bulk materials in a simple single-pass geometry. The 75 fs, 210 nJ pulses from an amplified 76 MHz, 15.7 W Yb:KGW oscillator after sequential spectral broadening in ZnS and YAG samples of 2 mm and 15 mm thickness, respectively, were compressed to 37 fs by means of Gires–Tournois interferometric mirrors. The post-compressed pulses with an average power of 11.47 W demonstrated reasonable spatial-spectral homogeneity of the beam with the spectral overlap parameter and good beam quality with and .
Full article
(This article belongs to the Special Issue Advances in Ultrafast Laser Science and Applications)
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Open AccessArticle
Flexible Modulation of Perfect Vortex Beams by Combining Coherent Beams
by
Bowang Shu, Yuqiu Zhang, Hongxiang Chang, Shiqing Tang, Jinyong Leng, Jiangming Xu and Pu Zhou
Photonics 2024, 11(4), 385; https://doi.org/10.3390/photonics11040385 - 18 Apr 2024
Abstract
Perfect vortex beams (PVBs) possess the advantage of a stable light field distribution regardless of their topological charges, and thus they are extensively utilized in various applications, such as free-space optical communication, optical tweezers and laser processing. Herein, we report a new strategy
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Perfect vortex beams (PVBs) possess the advantage of a stable light field distribution regardless of their topological charges, and thus they are extensively utilized in various applications, such as free-space optical communication, optical tweezers and laser processing. Herein, we report a new strategy to generate and modulate PVBs using coherent beam combining (CBC) technology. Both piston phase and tilting phase controlling methods have been successfully employed, and the corresponding properties of the generated PVBs have been fully investigated. Moreover, the number and position of the gaps in fractional perfect vortex beams (FPVBs) could be precisely controlled, and the relationships between these modulated parameters and the performance of FPVBs are uncovered. These simulation analysis results demonstrate the potential for flexible modulation of PVBs or FPVBs in the CBC system, indicating promising prospects for coherent beam arrays (CBAs) in laser beam shaping and achieving high-power structured light.
Full article
(This article belongs to the Special Issue Recent Advances in Laser Beams)
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Open AccessArticle
Coherent Raman Scattering Spectral Shapes in a Strong Excitation Regime (Model Calculations)
by
Georgi B. Hadjichristov
Photonics 2024, 11(4), 384; https://doi.org/10.3390/photonics11040384 - 18 Apr 2024
Abstract
The influence of the interference between coherent processes in third-order nonlinear Raman scattering on the spectral shapes of Raman-scattered light waves is numerically modeled and discussed in the cases of commonly used coherent Raman spectroscopy techniques. The effects on the lineshapes depending on
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The influence of the interference between coherent processes in third-order nonlinear Raman scattering on the spectral shapes of Raman-scattered light waves is numerically modeled and discussed in the cases of commonly used coherent Raman spectroscopy techniques. The effects on the lineshapes depending on the laser intensity are analyzed for the coherent Raman spectroscopy performed via the excitation of molecular systems with focused laser pulses at high intensities. In this case, the interplay between the coherent processes in nonlinear Raman scattering, as well as laser power-induced resonance effects, may be significant and should be taken into account in the spectral lineshape analysis in coherent Raman spectroscopy and its related applications, since the coherent Raman spectra may be considerably modified.
Full article
(This article belongs to the Special Issue Advances in Nonlinear Optics: From Fundamentals to Applications)
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Open AccessArticle
Simulation Analysis of an Atmospheric Turbulence Wavefront Measurement System
by
Gangyu Wang, Laian Qin, Yang Li, Yilun Cheng, Xu Jing, Gongye Chen and Zaihong Hou
Photonics 2024, 11(4), 383; https://doi.org/10.3390/photonics11040383 - 18 Apr 2024
Abstract
In this paper, a turbulent wavefront measurement model based on the Hartmann system structure is proposed. The maximum recognizable mode number of different lens units is discussed, and the influence of different lens array arrangements on the accuracy of turbulent wavefront reconstruction is
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In this paper, a turbulent wavefront measurement model based on the Hartmann system structure is proposed. The maximum recognizable mode number of different lens units is discussed, and the influence of different lens array arrangements on the accuracy of turbulent wavefront reconstruction is analyzed. The results indicate that the increase in the aberration order of the turbulent wavefront has a certain influence on the reconstruction ability of the system. Different lens arrangements and number of lens units will lead to the effective reconstruction of different final mode orders. When using a 5 × 5 lens array arrangement and a hexagonal arrangement of 19 lenses, the maximum order of turbulent wavefront aberrations allowing for effective reconstruction was 25. When the sparse arrangement of 25 lenses or the sparse arrangement of 31 lenses was used, the maximum order allowing for effective reconstruction was 36. If the aberration composition of the turbulent wavefront contained higher-order aberrations, the system could not accurately measure the turbulent wavefront. When the order of the aberrations of the turbulent wavefront was low, the turbulent wavefront could be measured by the lens arrangement with fewer lens units, and the wavefront reconstruction accuracy was close to the measurement results obtained when more lens units were used.
Full article
(This article belongs to the Special Issue Optical Imaging and Measurements)
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Open AccessArticle
Synthesis of Aluminium Nitride-Based Coatings on Mild Steel Substrates Utilising an Integrated Laser/Sol–Gel Method
by
Ogulcan Eren, Alhaji M. Kamara, Huseyin Kursad Sezer and Sundar Marimuthu
Photonics 2024, 11(4), 382; https://doi.org/10.3390/photonics11040382 - 18 Apr 2024
Abstract
The field of protective coatings for industrial applications is continuously evolving, driven by a need for materials that offer exceptional hardness, enhanced wear resistance, and low friction coefficients. Conventional methods of coating development, such as physical vapour deposition (PVD) and chemical vapour deposition
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The field of protective coatings for industrial applications is continuously evolving, driven by a need for materials that offer exceptional hardness, enhanced wear resistance, and low friction coefficients. Conventional methods of coating development, such as physical vapour deposition (PVD) and chemical vapour deposition (CVD), often face challenges like the necessity of vacuum conditions, slow growth rates, and weak substrate adhesion, leading to inadequate interface bonding. This study introduces a novel approach utilising an integrated laser/sol–gel method for synthesising aluminium nitride (AlN) coatings on EN43 mild steel substrates which overcomes these limitations. The technique employs a high-intensity diode laser with optimal power and translation speeds to consolidate a pre-applied thin layer of sol–gel slurry consisting of aluminium hydroxide, graphite, and urea on the substrate. Chemical thermodynamic calculations were used to predict the slurry composition, along with identifying the critical temperature range and the essential enthalpy needed for the synthesis of aluminium nitride. A three-dimensional heat transfer model was developed to predict the important process parameters, such as scanning speed and laser power density, required to achieve the temperature ranges necessary for a successful deposition process. Optical and scanning electron microscopy techniques were used to examine the surface morphology and microstructure of the coating. Elemental energy-dispersive X-ray spectroscopy and an X-ray diffraction analysis confirmed the synthesis of an aluminium nitride coating with a thickness ranging from 4 to 5 µm. Furthermore, the detection of sub-micron crystalline aluminium nitride structures yielding a metal matrix composite interlayer was indicative of strong metallurgical bonding. Microhardness testing indicated a hardness value of approximately 876 HV. The coated samples with the highest quality exhibited a surface roughness, Ra, ranging from 1.8 to 2.1 µm. Additionally, the coatings demonstrated an exceptionally low coefficient of friction, recorded at less than 0.1. These results represent a significant step forward in this field, offering a cost-effective, efficient, and scalable solution for producing high-quality coatings with superior performance characteristics.
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(This article belongs to the Special Issue Laser Processing and Modification of Materials)
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Optical Design of a Wavelength Selective Switch Utilizing a Waveguide Frontend with Beamsteering Capability
by
Georgios Patsamanis, Dimitra Ketzaki, Dimitrios Chatzitheocharis and Konstantinos Vyrsokinos
Photonics 2024, 11(4), 381; https://doi.org/10.3390/photonics11040381 - 18 Apr 2024
Abstract
Wavelength selective switches (WSSs) are essential elements for wavelength division multiplexing (WDM) optical networks, as they offer cost-effective, high port-count and flexible spectral channel switching. This work proposes a new hybrid WSS architecture that leverages the beam shaping and steering features of uniform
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Wavelength selective switches (WSSs) are essential elements for wavelength division multiplexing (WDM) optical networks, as they offer cost-effective, high port-count and flexible spectral channel switching. This work proposes a new hybrid WSS architecture that leverages the beam shaping and steering features of uniform silicon nitride-based end-fire optical phased arrays (OPAs). By introducing beamforming to a WSS system, the spectral channels on the liquid crystal on silicon (LCoS) panel can be tailored and arranged properly, depending on the optical configuration, using the beam control capabilities of OPAs. Combining 3D-FDTD and ray tracing simulations, the study shows that, by reducing the input beam dimensions with proper sizing of the OPAs, the WSS design with a null-steering OPA layout and 4 × No switch size features increased spectral resolution. This extensive beamforming study on the steering-enabled layout reveals the acquirement of an even higher input channel number, matching the 8 × No WSS scheme, with flexible channel routing on the LCoS panel. Such implementation of beamsteerers can unlock an extra degree of freedom for the switching capabilities of hybrid WSS devices. The results show great promise for the introduction of OPAs in WSS systems and provide valuable insight for the design of future wireless communication links and WDM systems.
Full article
(This article belongs to the Special Issue Optical Communication and Networks Facilitating Emerging Applications and Services)
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Open AccessArticle
Sensitive Detection of Silicon in Aqua Phase by Microwave-Assisted Laser-Induced Breakdown Spectroscopy
by
Ali M. Alamri and Zeyad T. Alwahabi
Photonics 2024, 11(4), 380; https://doi.org/10.3390/photonics11040380 - 17 Apr 2024
Abstract
Microwave-assisted laser-induced breakdown spectroscopy (MA-LIBS) was demonstrated to be an effective method for the quantitative detection of silicon in the aqua phase. Microwave radiation was transmitted into plasma using a near-field applicator device under ambient pressure and temperature conditions. Silicon detection was performed
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Microwave-assisted laser-induced breakdown spectroscopy (MA-LIBS) was demonstrated to be an effective method for the quantitative detection of silicon in the aqua phase. Microwave radiation was transmitted into plasma using a near-field applicator device under ambient pressure and temperature conditions. Silicon detection was performed directly on the surface of a water jet. Two Si emission lines, 251.6 nm and 288.16 nm, were selected to evaluate the MA-LIBS enhancement and determine the limit of detection for silicon. The signal-to-noise ratio of the MA-LIBS spectra was investigated as a function of laser energy and microwave power. The calibration curve was established for Si quantitative analysis using 8 mJ of laser energy and 900 W of microwave power. The MA-LIBS recorded a 51-fold and 77-fold enhancement for Si I 251.6 nm and 288.16 nm, respectively. Reducing liquid splashes after laser ablation is essential to improving the quantitative analysis. Using MA-LIBS reduced the liquid splashes due to MA-LIBS using 8 mJ. The detection limit achieved was 1.25, a 16-fold improvement over traditional LIBS.
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(This article belongs to the Special Issue Sensitive Laser Spectroscopy)
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Open AccessFeature PaperReview
Revisiting Poincaré Sphere and Pauli Algebra in Polarization Optics
by
Tiberiu Tudor and Gabriel Voitcu
Photonics 2024, 11(4), 379; https://doi.org/10.3390/photonics11040379 - 17 Apr 2024
Abstract
We present one of the main lines of development of Poincaré sphere representation in polarization optics, by using largely some of our contributions in the field. We refer to the action of deterministic devices, specifically the diattenuators, on the partial polarized light. On
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We present one of the main lines of development of Poincaré sphere representation in polarization optics, by using largely some of our contributions in the field. We refer to the action of deterministic devices, specifically the diattenuators, on the partial polarized light. On one hand, we emphasize the intimate connection between the Pauli algebraic analysis and the Poincaré ball representation of this interaction. On the other hand, we bring to the foreground the close similarity between the law of composition of the Poincaré vectors of the diattenuator and of polarized light and the law of composition of relativistic admissible velocities. These two kinds of vectors are isomorphic, and they are “imprisoned” in a sphere of finite radius, standardizable at a radius of one, i.e., Poincaré sphere.
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(This article belongs to the Special Issue Polarization Optics)
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Open AccessCommunication
Impact of Motion Characteristics of Airborne Platforms on the Performance of Space Laser Communication Links
by
Xin Zhang, Shiming Gao, Zhi Liu, Qingfang Jiang, Lixin Meng, Helong Wang and Keyan Dong
Photonics 2024, 11(4), 378; https://doi.org/10.3390/photonics11040378 - 17 Apr 2024
Abstract
When a platform carrying a space laser communication system moves through the atmosphere, the relative motion of the turret and the air produces fluctuations in the air density, which affects the beam propagation, and, hence, the laser communication performance. In this paper, we
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When a platform carrying a space laser communication system moves through the atmosphere, the relative motion of the turret and the air produces fluctuations in the air density, which affects the beam propagation, and, hence, the laser communication performance. In this paper, we propose a performance analysis method for the space laser communication link to the airborne platform. By employing this method, which is based on a flow field simulation, we are able to determine the laser link’s communication performance curves for various flying situations. At an altitude of 5 km and a signal-to-noise ratio (SNR) of 10 dB for the laser communication link, the bit error rate (BER) under a flight speed of 0.4 Mach is . With each 0.1 Mach increase in speed, the BER decreases by approximately . If the flight speed is 0.8 Mach and the flight altitude increases from 5 km to 10 km, the BER decreases from to , but the system becomes more sensitive to changes in flight speed. Under the same flight altitude conditions, the beam spot on the downwind side is more affected by airflow, resulting in a general increase in the BER by approximately one order of magnitude, compared to the upwind side.
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(This article belongs to the Section Optoelectronics and Optical Materials)
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Open AccessArticle
Agreement on Anterior Chamber Depth Measurement between Three Commercially Available Devices
by
Veronica Noya-Padin, Hugo Pena-Verdeal, Jacobo Garcia-Queiruga, Irene Sampedro-Mariño, Maria Jesus Giraldez and Eva Yebra-Pimentel
Photonics 2024, 11(4), 377; https://doi.org/10.3390/photonics11040377 - 17 Apr 2024
Abstract
The present study aimed to assess the agreement of three commercially available devices on the measurement of anterior chamber depth (ACD) with and without compensation by central corneal thickness measurement (CCT). Fifty eyes were included in an observational cross-sectional study. Participants underwent a
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The present study aimed to assess the agreement of three commercially available devices on the measurement of anterior chamber depth (ACD) with and without compensation by central corneal thickness measurement (CCT). Fifty eyes were included in an observational cross-sectional study. Participants underwent a single visit during which devices were used to obtain the inclusion/exclusion (ARK510A, Canon TX-10) and studied (VX-120, Lenstar LS900 and EchoScan US-800) parameters. Based on invasiveness, tests were always performed in the same order by one researcher (to avoid inter-observer variability) and only in the right eye (to avoid overstating the precision of estimates) in each participant. The keratometry, autorefraction, intraocular pressure and anterior chamber angle values were used as inclusion criteria, while the CCT and ACD values were used in the agreement analysis between devices. There was a general and a paired difference in ACD measurements between devices (Greenhouse–Geisser: p ≤ 0.001; Sidak: all p ≤ 0.001). No significant difference was found in ACD measurements compensated by CCT values between the devices (Greenhouse–Geisser: p = 0.200). Pairwise analysis showed a significant difference in VX-120 vs. Lenstar (Sidak: p = 0.021). The differences in ACD measurements compensated by CCT values between the devices were clinically acceptable. Consequently, using these instruments interchangeably in daily routines based on this correction is justified.
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(This article belongs to the Special Issue Latest Developments in Ocular Biometry)
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Open AccessCommunication
Time-Division Multiplexed Optical Covert Communication System Based on Gain-Switched Optical Pulses
by
Dong Liu, Yongliang Yin, Mingyu Cui, Zhanqi Liu and Huatao Zhu
Photonics 2024, 11(4), 376; https://doi.org/10.3390/photonics11040376 - 17 Apr 2024
Abstract
In optical covert communication systems based on gain-switched distributed feedback semiconductor lasers, the trade-off between the modulation frequency and the spectral imperceptibility limits the bit rate of the secure channel. To improve the system performance in terms of the bit rate and covertness,
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In optical covert communication systems based on gain-switched distributed feedback semiconductor lasers, the trade-off between the modulation frequency and the spectral imperceptibility limits the bit rate of the secure channel. To improve the system performance in terms of the bit rate and covertness, optical time-division multiplexing is introduced to optical covert communication for the first time. The optical time-division multiplexed covert channel can work under both multiple-user and single-user conditions. The optical time-division multiplexed covert communication system is demonstrated via a system simulation. The results show that the covertness is enhanced by the optical time-division multiplexing in the spectral domain. The receiver sensitivity of the multiple-user condition is lower than the single-user one.
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(This article belongs to the Section Optical Communication and Network)
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Open AccessArticle
Damascene Process Development for Low-Loss Photonics Devices with Applications in Frequency Comb
by
Qiaoling Zhou, Yejia Jin, Shaonan Zheng, Xingyan Zhao, Yang Qiu, Lianxi Jia, Yuan Dong, Qize Zhong and Ting Hu
Photonics 2024, 11(4), 375; https://doi.org/10.3390/photonics11040375 - 16 Apr 2024
Abstract
Silicon nitride (SiN) is emerging as a material of choice for photonic integrated circuits (PICs) due to its ultralow optical losses, absence of two-photon absorption in telecommunication bands, strong Kerr nonlinearity and high-power handling capability. These properties make SiN particularly well-suited for applications
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Silicon nitride (SiN) is emerging as a material of choice for photonic integrated circuits (PICs) due to its ultralow optical losses, absence of two-photon absorption in telecommunication bands, strong Kerr nonlinearity and high-power handling capability. These properties make SiN particularly well-suited for applications such as delay lines, chip-scale frequency combs and narrow-linewidth lasers, especially when implemented with thick SiN waveguides, which is achieved through low-pressure chemical vapor deposition (LPCVD). However, a significant challenge arises when the LPCVD SiN film thickness exceeds 300 nm on an 8-inch wafer, as this can result in cracking due to high stress. In this work, we successfully develop a damascene process to fabricate 800 nm-thick SiN photonics devices on an 8-inch wafer in a pilot line, overcoming cracking challenges. The resulting 2 × 2 multimode interference (MMI) coupler exhibits low excess loss (−0.1 dB) and imbalance (0.06 dB) at the wavelength of 1310 nm. Furthermore, the dispersion-engineered SiN micro-ring resonator exhibits a quality (Q) factor exceeding 1 × 106, enabling the generation of optical frequency combs. Our demonstration of photonics devices utilizing the photonics damascene process sets the stage for high-volume manufacturing and widespread deployment.
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(This article belongs to the Section Optoelectronics and Optical Materials)
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Open AccessArticle
Specific and Simultaneous Detection of E. coli O157:H7 and Shiga-like Toxins Using a Label-Free Photonic Immunosensor
by
Ana Fernández, Manuel Hernández, Yolanda Moreno and Jorge García-Hernández
Photonics 2024, 11(4), 374; https://doi.org/10.3390/photonics11040374 - 16 Apr 2024
Abstract
The current study outlines the advancement of an innovative technique for the simultaneous detection of E. coli O157:H7 and its Shiga-like toxins in food samples by utilizing a photonic label-free biosensor coupled with a microfluidic system. This detection method relies on ring resonator
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The current study outlines the advancement of an innovative technique for the simultaneous detection of E. coli O157:H7 and its Shiga-like toxins in food samples by utilizing a photonic label-free biosensor coupled with a microfluidic system. This detection method relies on ring resonator transduction that is functionalized with specific bioreceptors against O157:H7 on silicon nitride surfaces capable of binding specifically to the antigen bacterium and its verotoxins. This experiment included the characterization of selected monoclonal and polyclonal antibodies employed as detection probes through ELISA immunoassays exposed to target bacterial antigens. A thorough validation of photonic immunosensor detection was conducted on inoculated minced beef samples using reference standards for E. coli O157:H7 and its verotoxins (VTx1 and VTx2) and compared to gold-standard quantification. The lowest limit-of-detection values of 10 CFU/mL and 1 ppm were achieved for the detection of bacteria and its verotoxins. In this study, the lowest limit of quantification (LoQ) achieved for bacterial quantification was 100 CFU/mL, and, for verotoxins, it was 2 ppm. This study confirmed the effectiveness of a new quality control and food hygiene method, demonstrating the rapid and sensitive detection of E. coli O157:H7 and its verotoxins. This innovative approach has the potential to be applied in food production environments.
Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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Open AccessCommunication
Study of Optical Rogue Waves in Two-Dimensional Disordered Lattices
by
Jie Song, Meng Li, Fuqiang Li, Ying Wang, Ziyang Chen and Cibo Lou
Photonics 2024, 11(4), 373; https://doi.org/10.3390/photonics11040373 - 16 Apr 2024
Abstract
We probed the impact of both the degree of disorder and nonlinearity on rogue waves (RWs) in two-dimensional disordered lattices. Our results unveiled that an increase in the disorder level under linear conditions heightened the probability of RW occurrence and simultaneously contracted the
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We probed the impact of both the degree of disorder and nonlinearity on rogue waves (RWs) in two-dimensional disordered lattices. Our results unveiled that an increase in the disorder level under linear conditions heightened the probability of RW occurrence and simultaneously contracted the “long tail”. Interestingly, with the introduction of nonlinearity, this “long tail” became shorter compared with linear conditions. Nevertheless, in the context of disordered media, RW occurrence probability demonstrated relative stability—a distinct deviation from its conduct within homogeneous media.
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(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)
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Open AccessArticle
Structural, Mechanical, and Optoelectronic Properties of CH3NH3PbI3 as a Photoactive Layer in Perovskite Solar Cell
by
Elkana K. Rugut, Nnditshedzeni E. Maluta, Regina R. Maphanga, Refilwe E. Mapasha and Joseph K. Kirui
Photonics 2024, 11(4), 372; https://doi.org/10.3390/photonics11040372 - 16 Apr 2024
Abstract
The structural, electronic, mechanical, and optical properties of pseudo-cubic CH3NH3PbI3 perovskite have been studied within the framework of density functional theory, in line with solar cell applications. The computed values of lattice and elastic constants concurred with the
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The structural, electronic, mechanical, and optical properties of pseudo-cubic CH3NH3PbI3 perovskite have been studied within the framework of density functional theory, in line with solar cell applications. The computed values of lattice and elastic constants concurred with the available theoretical and experimental data. This compound has a semi-conducting behavior, with a direct band gap of about 1.49 eV. Note that the solar radiation spectrum has a maximum energy intensity value of approximately 1.50 eV. Thus, semiconductors with such gaps are preferred for photovoltaic applications. Its elastic parameters reveal that it is a ductile material that is mechanically stable. Optical descriptors such as refractive index, reflectivity, extinction, energy loss, and absorption have been explored with the aim of establishing the optical features of the material. Our findings demonstrate that this perovskite is suitable for solar cell applications based on the size and nature of the band gap, as also supported by the obtained upper limit value of simulated power conversion efficiency via the spectroscopic limited maximum efficiency mathematical model.
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(This article belongs to the Section Optoelectronics and Optical Materials)
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