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Photonics, Volume 11, Issue 6 (June 2024) – 89 articles

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9 pages, 243 KiB  
Article
Few ns Pulse Duration of Gain-Switched Ho:YAG Laser Pumped by an Active Q-Switched Tm:YLF Laser
by Shaul Avichai Golan, Rotem Nahear, Yechiel Bach and Salman Noach
Photonics 2024, 11(6), 572; https://doi.org/10.3390/photonics11060572 (registering DOI) - 18 Jun 2024
Viewed by 53
Abstract
This paper describes a gain-switched Ho:YAG laser that emitted at 2089 nm, driven by an actively Q-switched Tm:YLF laser as the pumping source. The laser attained few ns short pulse durations with high energies at controlled repetition rates due to the active Q-switch [...] Read more.
This paper describes a gain-switched Ho:YAG laser that emitted at 2089 nm, driven by an actively Q-switched Tm:YLF laser as the pumping source. The laser attained few ns short pulse durations with high energies at controlled repetition rates due to the active Q-switch pump source. Using the gain-switch method, stable short pulse durations ranging from 3.5 to 7.2 ns, with an energy per pulse of 0.4 to 0.52 mJ, were achieved at repetition rates of up to 2.5 kHz. This design can have significant advantages in various fields, where accuracy in the repetition rate is essential and a passive Q-switch cannot be implemented due to its accuracy limitations, including sensing, LIDAR, medical procedures, and material processing. Full article
(This article belongs to the Special Issue Laser Technology and Applications)
12 pages, 6701 KiB  
Article
Full Stokes Mid-Wavelength Infrared Polarization Photodetector Based on the Chiral Dielectric Metasurface
by Bo Cheng, Yuxiao Zou and Guofeng Song
Photonics 2024, 11(6), 571; https://doi.org/10.3390/photonics11060571 (registering DOI) - 18 Jun 2024
Viewed by 97
Abstract
Conventional imaging techniques can only record the intensity of light while polarization imaging can record the polarization of light, thus obtaining a higher dimension of image information. We use the COMSOL software to numerically propose a circular polarization photodetector composed of the dislocated [...] Read more.
Conventional imaging techniques can only record the intensity of light while polarization imaging can record the polarization of light, thus obtaining a higher dimension of image information. We use the COMSOL software to numerically propose a circular polarization photodetector composed of the dislocated 2-hole Si chiral metasurfaces controlling the circular polarization lights and the HgCdTe (MCT) photodetector chip to detect the intensity of light signals. The chiral metasurfaces can be equated to a significant radiation source of the Z-type current density under the right circularly polarized incidence conditions, which explains the large circular dichroism (CD) of absorption of 95% in chiral photodetectors. In addition, the linear dichroism (LD) of the linear polarization pixel is 0.62, and the extinction ratio (ER) is 21 dB. The full Stokes pixel using the six-image-element technique can almost measure arbitrary polarization information of light at 4 μm operation wavelength. Our results highlight the potential of circular dichroic metasurfaces as photonic manipulation platforms for miniaturized polarization detectors. Full article
(This article belongs to the Special Issue Design and Applications of Polarized Optical System)
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8 pages, 3159 KiB  
Communication
High-Power GHz Burst-Mode All-Fiber Laser System with Sub 300 fs Pulse Duration
by Feng Li, Wei Zhao, Yuxi Fu, Jixin Xing, Wenlong Wen, Lei Wang, Qianglong Li, Xue Cao, Hualong Zhao and Yishan Wang
Photonics 2024, 11(6), 570; https://doi.org/10.3390/photonics11060570 (registering DOI) - 18 Jun 2024
Viewed by 91
Abstract
An all-fiber low-repetition-rate SESAM mode-locked fiber oscillator combined with a dispersion-managed active fiber loop produces a flexible GHz burst-mode laser source. The high-power output is then produced by amplifying the GHz burst-mode laser source using an all-fiber chirped-pulse amplification system. Then, the laser [...] Read more.
An all-fiber low-repetition-rate SESAM mode-locked fiber oscillator combined with a dispersion-managed active fiber loop produces a flexible GHz burst-mode laser source. The high-power output is then produced by amplifying the GHz burst-mode laser source using an all-fiber chirped-pulse amplification system. Then, the laser is compressed using a grating pair compressor; a maximum amplified power of 97 W is obtained. This results in a compressed high power of 82.07 W with a power stability RMS of 0.09% and beam quality better than 1.2. Accurate dispersion control allows for the production of a high-quality pulse duration of 265 fs. Full article
(This article belongs to the Special Issue Advanced Lasers and Their Applications II)
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18 pages, 15762 KiB  
Article
Physics-Based Practical Speckle Noise Modeling for Optical Coherence Tomography Image Denoising
by Lei Yang, Di Wu, Wenteng Gao, Ronald X. Xu and Mingzhai Sun
Photonics 2024, 11(6), 569; https://doi.org/10.3390/photonics11060569 - 17 Jun 2024
Viewed by 179
Abstract
Optical coherence tomography (OCT) has been extensively utilized in the field of biomedical imaging due to its non-invasive nature and its ability to provide high-resolution, in-depth imaging of biological tissues. However, the use of low-coherence light can lead to unintended interference phenomena within [...] Read more.
Optical coherence tomography (OCT) has been extensively utilized in the field of biomedical imaging due to its non-invasive nature and its ability to provide high-resolution, in-depth imaging of biological tissues. However, the use of low-coherence light can lead to unintended interference phenomena within the sample, which inevitably introduces speckle noise into the imaging results. This type of noise often obscures key features in the image, thereby reducing the accuracy of medical diagnoses. Existing denoising algorithms, while removing noise, tend to also damage the structural details of the image, affecting the quality of diagnosis. To overcome this challenge, we have proposed a speckle noise (PSN) framework. The core of this framework is an innovative dual-module noise generator that can decompose the noise in OCT images into speckle noise and equipment noise, addressing each type independently. By integrating the physical properties of noise into the design of the noise generator and training it with unpaired data, we are able to synthesize realistic noise images that match clear images. These synthesized paired images are then used to train a denoiser to effectively denoise real OCT images. Our method has demonstrated its superiority in both private and public datasets, particularly in maintaining the integrity of the image structure. This study emphasizes the importance of considering the physical information of noise in denoising tasks, providing a new perspective and solution for enhancing OCT image denoising technology. Full article
(This article belongs to the Section Biophotonics and Biomedical Optics)
14 pages, 3246 KiB  
Article
Nanosensor Based on the Circular Ring with External Rectangular Ring Structure
by Shuwen Chang, Shubin Yan, Yiru Su, Jin Wang, Yuhao Cao, Yi Zhang, Taiquan Wu and Yifeng Ren
Photonics 2024, 11(6), 568; https://doi.org/10.3390/photonics11060568 - 17 Jun 2024
Viewed by 137
Abstract
This paper presents a novel nanoscale refractive index sensor, which is produced by using a metal–insulator–metal (MIM) waveguide structure coupled with the circular ring with an external rectangular ring (CRERR) structure with the Fano resonance phenomenon. In this study, COMSOL software was used [...] Read more.
This paper presents a novel nanoscale refractive index sensor, which is produced by using a metal–insulator–metal (MIM) waveguide structure coupled with the circular ring with an external rectangular ring (CRERR) structure with the Fano resonance phenomenon. In this study, COMSOL software was used to model and simulate the structure, paired with an analysis of the output spectra to detail the effect of constructional factors on the output Fano curve as measured from a finite element method. After a series of studies, it was shown that an external rectangular ring is the linchpin of the unsymmetrical Fano resonance, while the circular ring’s radius strongly influences the transducer’s capability to achieve a maximum for 3180 nm/RIU sensitivity and a FOM of 54.8. The sensor is capable of achieving sensitivities of 0.495 nm/mgdL−1 and 0.6375 nm/mgdL−1 when detecting the concentration of the electrolyte sodium and potassium ions in human blood and is expected to play an important role in human health monitoring. Full article
(This article belongs to the Special Issue New Perspectives in Optical Design)
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12 pages, 2673 KiB  
Article
A Study on the Irradiance Scintillation Characteristics of Monochromatic LED-Based Visible Light Communication Systems in Weak-to-Strong Turbulence
by Yao Ji, Wensheng Chen, Danning Wang and Chen Cheng
Photonics 2024, 11(6), 567; https://doi.org/10.3390/photonics11060567 - 17 Jun 2024
Viewed by 212
Abstract
Atmospheric turbulence causes transmitted light to fade randomly, which results in irradiance scintillation fluctuations in the received signal and significantly affects the quality of wireless optical communication systems. In this paper, we investigate the propagation characteristics of a monochromatic light-emitting diode (LED) light [...] Read more.
Atmospheric turbulence causes transmitted light to fade randomly, which results in irradiance scintillation fluctuations in the received signal and significantly affects the quality of wireless optical communication systems. In this paper, we investigate the propagation characteristics of a monochromatic light-emitting diode (LED) light beam through weak-to-strong turbulence. Considering the spatial incoherence of a monochromatic LED light source, the emitted light field of a monochromatic LED light source is represented by a random field multiplied by a deterministic field that follows a Gaussian distribution. Then, based on the extended-Rytov theory, a closed expression for the irradiance scintillation index under weak-to-strong turbulence is derived. In addition, the expression for the fading probability governed by the Gamma–Gamma model is given. Finally, the effects of near-earth atmospheric refractive index structural parameters, signal propagation distances, and working light wavelengths on propagation characteristics of the LED-based VLC system are simulated and compared with those of the laser-based one. The results theoretically confirm that laser light sources are more susceptible to atmospheric turbulence along the propagation path than monochromatic LED light sources. The investigation in this paper can provide theoretical support for the design of visible light communication systems in practical applications. Full article
(This article belongs to the Special Issue Optical Light Propagation and Communication Through Turbulent Medium)
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10 pages, 1738 KiB  
Article
An Effective Model for Capturing the Role of Excitonic Interactions in the Wave-Packet Dynamics of DNA Nucleobases
by Tong Guan, Ajay Jha, Pan-Pan Zhang and Hong-Guang Duan
Photonics 2024, 11(6), 566; https://doi.org/10.3390/photonics11060566 - 17 Jun 2024
Viewed by 143
Abstract
Investigating exciton dynamics within DNA nucleobases is essential for comprehensively understanding how inherent photostability mechanisms function at the molecular level, particularly in the context of life’s resilience to solar radiation. In this paper, we introduce a mathematical model that effectively simulates the photoexcitation [...] Read more.
Investigating exciton dynamics within DNA nucleobases is essential for comprehensively understanding how inherent photostability mechanisms function at the molecular level, particularly in the context of life’s resilience to solar radiation. In this paper, we introduce a mathematical model that effectively simulates the photoexcitation and deactivation dynamics of nucleobases within an ultrafast timeframe, particularly focusing on wave-packet dynamics under conditions of strong nonadiabatic coupling. Employing the hierarchy equation of motion, we simulate two-dimensional electronic spectra (2DES) and calibrate our model by comparing it with experimentally obtained spectra. This study also explores the effects of base stacking on the photo-deactivation dynamics in DNA. Our results demonstrate that, while strong excitonic interactions between nucleobases are present, they have a minimal impact on the deactivation dynamics of the wave packet in the electronic excited states. We further observe that the longevity of electronic excited states increases with additional base stacking and pairing, a phenomenon accurately depicted by our excitonic model. This model enables a detailed examination of the wave packet’s motion on electronic excited states and its rapid transition to the ground state. Additionally, using this model, we studied base stacks in DNA hairpins to effectively capture the primary exciton dynamics at a reasonable computational scale. Overall, this work provides a valuable framework for studying exciton dynamics from single nucleobases to complex structures such as DNA hairpins. Full article
(This article belongs to the Special Issue Ultrafast Optics and Applications)
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13 pages, 12033 KiB  
Article
Ytterbium-Doped Double-Clad Fiber with High Uniformity of Concentration Distribution and Suppressed Photodarkening
by Yongqing Yi, Yize Shen, Pengcheng Geng, Rong Pan, Shijie Xu and Ruifang Luo
Photonics 2024, 11(6), 565; https://doi.org/10.3390/photonics11060565 - 17 Jun 2024
Viewed by 245
Abstract
Photodarkening (PD) effect in ytterbium-doped fiber (YDF) has a significant impact on the high-power operational stability of fiber lasers, which seriously hinders the power scaling. In this paper, the relationship between ytterbium ions uniformity and the photodarkening effect in the YDF was investigated, [...] Read more.
Photodarkening (PD) effect in ytterbium-doped fiber (YDF) has a significant impact on the high-power operational stability of fiber lasers, which seriously hinders the power scaling. In this paper, the relationship between ytterbium ions uniformity and the photodarkening effect in the YDF was investigated, and the fabrication process allowing improving the ytterbium ions uniformity in the core of preforms for suppressing the photodarkening effect was developed. The Modified Chemical Vapor Deposition (MCVD) method combined with Chelate Vapor Deposition (CVD) technology was adopted for multi-layer fiber core deposition, and an all-gas-phase technical process was proposed to improve the ytterbium ions uniformity in the Al/P co-doped glass matrix. The 25/400 μm YDFs obtained by this technology achieved stable 3.5 kW laser output power for 8 h with suppressed PD and nonlinear effects. Full article
(This article belongs to the Special Issue The Emerging Science and Applications of Fiber Laser Technology)
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25 pages, 13354 KiB  
Article
Design of a Continuous-Zoom 2D/3D Microscope with High Zoom Ratio and Full Field of View
by Yangshen Gong, Fei Li, Jiebo Huang, Jiaying He, Feihong Yu and Tingyu Zhao
Photonics 2024, 11(6), 564; https://doi.org/10.3390/photonics11060564 - 16 Jun 2024
Viewed by 317
Abstract
A four-group mechanically compensated continuous-zoom microscope is proposed and designed based on the theory of continuous zoom. The system addresses the limitations of traditional continuous-zoom microscopes, including a small zoom ratio, a short working distance, and the loss of details during 2D–3D switching. [...] Read more.
A four-group mechanically compensated continuous-zoom microscope is proposed and designed based on the theory of continuous zoom. The system addresses the limitations of traditional continuous-zoom microscopes, including a small zoom ratio, a short working distance, and the loss of details during 2D–3D switching. The system has a magnification of 0.6×~6.0× under two-dimensional observation, adapts to two-third-inch sensors, has a working distance of 130 mm, and adds a 360-degree rotatable beamsplitter for three-dimensional full-field-of-view observation. The magnification, numerical aperture, and sensor dimensions remain unchanged under both two-dimensional and three-dimensional observation. The design results demonstrate that the system is capable of achieving a high zoom ratio of 10× while maintaining a high level of imaging quality in both two-dimensional and three-dimensional modes. The MTF curves for each magnification are in close proximity to the diffraction limit, the spot diagrams are smaller than the airy disk range, and the zoom cam curves are smooth with no inflection points. Furthermore, the system negates the visual discrepancies and loss of detail that arise when switching observation modes due to alterations in system magnification and numerical aperture, thereby broadening the scope of applications for continuous-zoom microscopes. Full article
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12 pages, 2832 KiB  
Article
Generating Optical Vortex Array Laser Beams of Superimposing Hermite–Gaussian Beams with a Dual–Phase Modulation Digital Laser System
by Ly Ly Nguyen Thi, Ko-Fan Tsai and Shu-Chun Chu
Photonics 2024, 11(6), 563; https://doi.org/10.3390/photonics11060563 - 15 Jun 2024
Viewed by 242
Abstract
This study presents an efficient and practical intra-cavity approach for selectively generating vortex array laser beams employing a dual-phase modulation digital laser system, which has not yet been completed in single-phase modulation digital laser. The stable optical vortex array laser beams were formed [...] Read more.
This study presents an efficient and practical intra-cavity approach for selectively generating vortex array laser beams employing a dual-phase modulation digital laser system, which has not yet been completed in single-phase modulation digital laser. The stable optical vortex array laser beams were formed by superimposing cavity Hermite–Gaussian (HG) eigenmodes. In particular, when the selected cavity HG modes shared the same Gouy phase, the resulting optical vortex beam could preserve its light field pattern, thereby maintaining the optical vortex properties in the near and far fields. Numerical results demonstrated that employing dual-phase modulation could establish optimal boundary conditions for the selection of HG modes within the cavity, successfully generating various vortex array laser beams. The experimental validation of the proposed method confirmed the ability to select optical vortex array lasers solely by controlling the loaded phase of the dual-phase modulation digital laser. These results demonstrate the ability of digital lasers to generate and dynamically control optical vortex array lasers. Full article
(This article belongs to the Special Issue Optical Vortex Laser)
18 pages, 1564 KiB  
Article
Propagation of a Partially Coherent Bessel–Gaussian Beam in a Uniform Medium and Turbulent Atmosphere
by Igor Lukin and Vladimir Lukin
Photonics 2024, 11(6), 562; https://doi.org/10.3390/photonics11060562 - 14 Jun 2024
Viewed by 277
Abstract
In this paper, the coherent properties of partially coherent Bessel–Gaussian optical beams propagating through a uniform medium (free space) or a turbulent atmosphere are examined theoretically. The consideration is based on the analytical solution of the equation for the transverse second-order mutual coherence [...] Read more.
In this paper, the coherent properties of partially coherent Bessel–Gaussian optical beams propagating through a uniform medium (free space) or a turbulent atmosphere are examined theoretically. The consideration is based on the analytical solution of the equation for the transverse second-order mutual coherence function of the field of partially coherent optical radiation in a turbulent atmosphere. For the partially coherent Bessel–Gaussian beam, the second-order mutual coherence function of the source field is taken as a Gaussian–Schell model. In this approximation, we analyze the behavior of the coherence degree and the integral coherence scale of these beams as a function of the propagation pathlength, propagation conditions, and beam parameters, such as the radius of the Gauss factor of the beam, parameter of the Bessel factor of the beam, topological charge, and correlation width of the source field of partially coherent radiation. It was found that, as a partially coherent vortex Bessel–Gaussian beam propagates through a turbulent atmosphere, there appear not two (as might be expected: one due to atmospheric turbulence and another due to the partial coherence of the source field), but only one ring dislocation of the coherence degree (due to the simultaneous effect of both these factors on the optical radiation). In addition, it is shown that the dislocation of the coherence degree that significantly affects the beam coherence level is formed only for beams, for which the coherence width of the source field is larger than the diameter of the first Fresnel zone. Full article
(This article belongs to the Special Issue Recent Advances in Diffractive Optics)
14 pages, 10209 KiB  
Article
Generalized-Mode Averaging Technique for Wrapped Phase
by Zhan Tang, Fengwei Liu and Yongqian Wu
Photonics 2024, 11(6), 561; https://doi.org/10.3390/photonics11060561 - 14 Jun 2024
Viewed by 247
Abstract
In this paper, a generalized-mode phase averaging technique is proposed to suppress air turbulence and random noise in optical shop testing. This approach eliminates the need to repeatedly unwrap and thus greatly improves processing efficiency. By removing the random tilt component of the [...] Read more.
In this paper, a generalized-mode phase averaging technique is proposed to suppress air turbulence and random noise in optical shop testing. This approach eliminates the need to repeatedly unwrap and thus greatly improves processing efficiency. By removing the random tilt component of the wrapped phase, a set of wrapped phases that are corrupted by random vibrations can be unified into the same mode, some of which obey a circular distribution. Therefore, the circular mean technique can be used for wrapped phase averaging; only one unwrapping process is required for a set of wrapped phases. A criterion based on maximum likelihood estimation is proposed to determine scenarios for the use of this method. The effects of noise and air disturbances on this method are discussed. Finally, the effectiveness of the method is demonstrated by simulations and experiments. Full article
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9 pages, 2039 KiB  
Article
Modulated Short-Time Fourier-Transform-Based Nonstationary Signal Decomposition for Dual-Comb Ranging Systems
by Ningning Han, Chao Wang, Zhiyang Wu, Xiaoyu Zhai, Yongzhen Pei, Haonan Shi and Xiaobo Li
Photonics 2024, 11(6), 560; https://doi.org/10.3390/photonics11060560 - 14 Jun 2024
Viewed by 261
Abstract
Analyzing and breaking down nonstationary signals into their primary components is significant in various optical applications. In this work, we design a direct, localized, and mathematically rigorous method for nonstationary signals by employing a modulated short-time Fourier transform (MSTFT) that can be implemented [...] Read more.
Analyzing and breaking down nonstationary signals into their primary components is significant in various optical applications. In this work, we design a direct, localized, and mathematically rigorous method for nonstationary signals by employing a modulated short-time Fourier transform (MSTFT) that can be implemented efficiently using fast Fourier transform, subsequently isolating energy-concentrated sets through an approximate threshold process, allowing us to directly retrieve instantaneous frequencies and signal components by determining the maximum frequency within each set. MSTFT provides a new insight into the time-frequency analysis in multicomponent signal separation and can be extended to other time-frequency transforms. Beyond the analysis of the synthetic, we also perform real dual-comb ranging signals under turbid water, and the results show an approximate 1.5 dB improvement in peak signal-to-noise ratio, further demonstrating the effectiveness of our method in challenging conditions. Full article
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10 pages, 3284 KiB  
Article
Simulation Study on Tunable Terahertz Bandpass Filter Based on Metal–Silicon–Metal Metasurface
by Wenjun Liu and Jitao Li
Photonics 2024, 11(6), 559; https://doi.org/10.3390/photonics11060559 - 13 Jun 2024
Viewed by 285
Abstract
Metasurface devices have demonstrated powerful electromagnetic wave manipulation capabilities. By adjusting the shape and size parameters of the metasurface microstructure, we can control the resonance between spatial electromagnetic waves and the metasurface, which will trigger wave scattering at a specific frequency. By utilizing [...] Read more.
Metasurface devices have demonstrated powerful electromagnetic wave manipulation capabilities. By adjusting the shape and size parameters of the metasurface microstructure, we can control the resonance between spatial electromagnetic waves and the metasurface, which will trigger wave scattering at a specific frequency. By utilizing these characteristics, we design a metasurface device with a bandpass filtering function and a unit cell of the metasurface consisting of a double-layer pinwheel-shaped metal structure and high resistance silicon substrate (forming metal–silicon–metal configuration). A bandpass filter operating in the terahertz band has been implemented, which achieves a 36 GHz filtering bandwidth when the transmission amplitude decreases by 3 dB and remains effective in a wave incidence angle of 20°. This work uses an equivalent RC resonance circuit to explain the formation of bandpass filtering. In addition, the photosensitive properties of silicon enable the filtering function of the device to have on/off tuned characteristics under light excitation, which enhances the dynamic controllability of the filter. The designed device may have application prospects in 6G space communication. Full article
(This article belongs to the Special Issue Metamaterials for Terahertz Photonics: Enabling Novel Techniques)
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10 pages, 1046 KiB  
Article
Time–Frequency and Spectrum Analyses of All-Solid-State Self-Mode-Locked Burst Pulse Lasers
by Mengmeng Xu, Miao Hu, Zerong Li, Jinxiu Wang, Jiaxin Fu, Shaokun Wang, Yingying Ji, Haozhen Li, Meihua Bi, Xuefang Zhou, Sunqiang Pan and Chong Liu
Photonics 2024, 11(6), 558; https://doi.org/10.3390/photonics11060558 - 13 Jun 2024
Viewed by 216
Abstract
The theoretical and experimental characteristics of all-solid-state self-mode-locked burst pulse lasers are investigated in this study. The time–frequency and spectrum analyses of the lasers incorporating Fabry–Pérot (F-P) structures are presented, along with the development of the corresponding theoretical model. Self-mode-locked burst pulse lasers [...] Read more.
The theoretical and experimental characteristics of all-solid-state self-mode-locked burst pulse lasers are investigated in this study. The time–frequency and spectrum analyses of the lasers incorporating Fabry–Pérot (F-P) structures are presented, along with the development of the corresponding theoretical model. Self-mode-locked burst pulse lasers are experimentally constructed to reduce intracavity losses using the front and rear end surfaces of the gain media to form F-P structures. When the laser cavity length is 600 mm and the gain media lengths are 5, 6, and 10 mm, each burst pulse produced contains 56, 47, and 28 subpulses, respectively, with the same burst pulse width of 2 ns. The burst pulse train with beam quality M2 = 1.37 and an average output power of 0.23 W is obtained when the gain medium length is 5 mm and the pump power is 4.5 W. The corresponding burst pulse repetition frequency is 0.25 GHz and the subpulse repetition frequency is 13.66 GHz. The time–frequency spectral analyses of the laser signals provide a good representation of laser spectral information that even the currently available highest-resolution spectrometers cannot resolve. Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
12 pages, 9879 KiB  
Article
Study on the Imaging Interference of a Vortex-Light-Modulated Gaussian Beam
by Yanghe Liu, Yuanhe Tang, Jian Zhou, Cunxia Li, Ningju Hui, Yishan Zhang and Yanlong Wang
Photonics 2024, 11(6), 557; https://doi.org/10.3390/photonics11060557 - 13 Jun 2024
Viewed by 272
Abstract
Combined with vortex light and airglow, some different physical phenomena are presented in this paper. Based on the ground-based airglow imaging interferometer (GBAII) made by our group, a liquid crystal on silicon (LCoS) device on one arm of a wide-angle Michelson interferometer (MI) [...] Read more.
Combined with vortex light and airglow, some different physical phenomena are presented in this paper. Based on the ground-based airglow imaging interferometer (GBAII) made by our group, a liquid crystal on silicon (LCoS) device on one arm of a wide-angle Michelson interferometer (MI) of the GBAII is replaced by the reflector mirror to become the GBAII-LCoS system. LCoS generates a vortex phase to convert a Gaussian profile airglow into a vortex light pattern. After the Gaussian profile vortex light equation is obtained by combining the Gaussian profile airglow with the Laguerre–Gauss light, three different physical phenomena are obtained: the simulated Gaussian vortex airglow beam exhibits a hollow phenomenon with the introduction of the vortex phase, and as the topological charge (TC) l increases, the hollow range also increases; after adding the vortex factor, the interference fringe intensity can be ‘broadened’ with the optical path difference (OPD) and TC l increases, which match the field broadening technology for solid wide-angle MI; the ‘Four-point algorithm’ wind measurement for the upper atmosphere based on the vortex airglow is derived, which is different from the usual expressions. Some experimental results are presented: We obtained the influence modes of vortex light interference and a polarization angle from 335° to 245°. We also obtained a series of interference images that verifies the rotation of the vortex light, onto which is loaded a set of superimposed vortex phase images with TC l = 3 into LCoS in turn, and the interference image is rotated under the condition of the polarization angle of 245°. The controlled vortex interference image for different TC and grayscale values are completed. Full article
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17 pages, 4307 KiB  
Article
High-Dynamic-Range Absorption Spectroscopy by Generating a Wide Path-Length Distribution with Scatterers
by Ayaka Mori, Kyohei Yamashita and Eiji Tokunaga
Photonics 2024, 11(6), 556; https://doi.org/10.3390/photonics11060556 - 13 Jun 2024
Viewed by 342
Abstract
In absorption spectroscopy, it is challenging to detect absorption peaks with significant differences in their intensity in a single measurement. We enable high-dynamic-range measurements by dispersing scatterers within a sample to create a broad distribution of path lengths (PLs). The sample is placed [...] Read more.
In absorption spectroscopy, it is challenging to detect absorption peaks with significant differences in their intensity in a single measurement. We enable high-dynamic-range measurements by dispersing scatterers within a sample to create a broad distribution of path lengths (PLs). The sample is placed within an integrating sphere (IS) to capture all scattered light of various PLs. To address the complexities of PLs inside the IS and the sample, we performed a ray-tracing simulation using the Monte Carlo (MC) method, which estimates the measured absorbance A and PL distribution from the sample’s absorption coefficient µa and scattering properties at each wavelength λ. This method was validated using dye solutions with two absorption peaks whose intensity ratio is 95:1, employing polystyrene microspheres (PSs) as scatterers. The results confirmed that both peak shapes were delineated in a single measurement without flattening the high absorption peak. Although the measured peak shapes A(λ) did not align with the actual peak shapes µa(λ), MC enabled the reproduction of µa(λ) from A(λ). Furthermore, the analysis of the PL distribution by MC shows that adding scatterers broadens the distribution and shifts it toward shorter PLs as absorption increases, effectively adjusting it to µa. Full article
(This article belongs to the Special Issue Photonics: 10th Anniversary)
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17 pages, 8273 KiB  
Article
High-Repetition-Rate 2.3–2.7 µm Acousto-Optically Tuned Narrow-Line Laser System Comprising Two Master Oscillators and Power Amplifiers Based on Polycrystalline Cr2+:ZnSe with the 2.1 µm Ho3+:YAG Pulsed Pumping
by Oleg Antipov, Ilya Eranov, Stanislav Balabanov, Anton Dobryinin, Yuri Getmanovskiy, Valeriy Sharkov and Nikolay Yudin
Photonics 2024, 11(6), 555; https://doi.org/10.3390/photonics11060555 - 12 Jun 2024
Viewed by 301
Abstract
High-average-power narrow-linewidth tunable solid-state lasers in the wavelength region between 2 and 3 μm are attractive light sources for many applications. This paper reports a narrow-linewidth widely tunable laser system based on the polycrystalline Cr2+:ZnSe elements pumped by repetitively pulsed 2.1 [...] Read more.
High-average-power narrow-linewidth tunable solid-state lasers in the wavelength region between 2 and 3 μm are attractive light sources for many applications. This paper reports a narrow-linewidth widely tunable laser system based on the polycrystalline Cr2+:ZnSe elements pumped by repetitively pulsed 2.1 µm Ho3+:YAG laser operating at a pulse rate of tens of kilohertz. An advanced procedure of ZnSe element doping and surface improvement was applied to increase the laser-induced damage threshold, which resulted in an increase in the output power of the Cr2+:ZnSe laser system. The high-average-power laser system comprised double master oscillators and power amplifiers: Ho3+:YAG and Cr2+:ZnSe laser oscillators, and Ho3+:YAG and Cr2+:ZnSe power amplifiers. The output wavelength was widely tuned within 2.3–2.7 µm by means of an acousto-optical tunable filter inside a Cr2+:ZnSe master oscillator cavity. The narrow-linewidth operation at the pulse repetition rate of 20–40 kHz in a high-quality beam with an average output power of up to 9.7 W was demonstrated. Full article
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11 pages, 7758 KiB  
Communication
Design of Channel Drop Filters Based on Photonic Crystal with a Dielectric Column with Large Radius inside Ring Resonator
by Ailing Zhang, Xiangyu Yang and Junfeng Wang
Photonics 2024, 11(6), 554; https://doi.org/10.3390/photonics11060554 - 12 Jun 2024
Viewed by 239
Abstract
Photonic crystal channel drop filters (CDFs) play a vital role in optical communication owing to their ability to drop the desired channel. However, it remains challenging to achieve high-efficiency CDFs. Here, we demonstrate a highly efficient three-channel CDF with both high transmission and [...] Read more.
Photonic crystal channel drop filters (CDFs) play a vital role in optical communication owing to their ability to drop the desired channel. However, it remains challenging to achieve high-efficiency CDFs. Here, we demonstrate a highly efficient three-channel CDF with both high transmission and high quality (Q) factor based on a novel ring resonator that is in the middle of two waveguides. A dielectric column with a large radius replaces the homogeneously distributed dielectric columns inside the ring cavity to modulate the coupling ratio with a straight waveguide, thereby enhancing the transmission and Q factor. The transmission and Q factor of the single-cavity filter are 99.7% and 12,798.4, respectively. The mean value of the three-channel filter based on the basic unit can reach up to 94.6% and 10,617, respectively, and a crosstalk between −30.16 and −50.61 dB is obtained. The proposed CDFs provide efficient filter capability, which reveals great potential in integrated optoelectronics and optical communication. Full article
(This article belongs to the Section Optoelectronics and Optical Materials)
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10 pages, 2387 KiB  
Article
Monte Carlo Simulation of Quantum-Cutting Nanocrystals as the Luminophore in Luminescent Solar Concentrators
by Qi Nie, Wenqing Li and Xiao Luo
Photonics 2024, 11(6), 553; https://doi.org/10.3390/photonics11060553 - 12 Jun 2024
Viewed by 252
Abstract
Quantum-cutting luminescent solar concentrators (QC-LSCs) have great potential to serve as large-area solar windows. These QC nanocrystals can realize a photoluminescence quantum yield (PLQY) of as high as 200% with virtually zero self-absorption loss. Based on our previous work, we have constructed a [...] Read more.
Quantum-cutting luminescent solar concentrators (QC-LSCs) have great potential to serve as large-area solar windows. These QC nanocrystals can realize a photoluminescence quantum yield (PLQY) of as high as 200% with virtually zero self-absorption loss. Based on our previous work, we have constructed a Monte Carlo simulation model that is suitable to simulate the performance of the QC-LSCs, which can take into account the band-edge emissions and near-infrared emissions of the QC-materials. Under ideal PLQY conditions, CsPbClxBr3−x:Yb3+-based LSCs can reach 12% of the size-independent external quantum efficiency (ηext). Even if LSCs have a certain scattering factor, the CsPbClxBr3−x:Yb3+-based LSCs can still obtain an ηext exceeding 6% in the window size (>1 m2). The flux gain (FG) of the CsPbClxBr3−x:Yb3+-based LSC-PV system can reach 14 in the window size, which is a very encouraging result. Full article
(This article belongs to the Special Issue New Insights in Low-Dimensional Optoelectronic Materials and Devices)
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12 pages, 1717 KiB  
Review
Methods Controlling Radiation Parameters of Mode-Locked All-Fiberized Lasers
by Sergey Kobtsev
Photonics 2024, 11(6), 552; https://doi.org/10.3390/photonics11060552 - 12 Jun 2024
Viewed by 267
Abstract
Fibre lasers are distinct in that their optical train is decoupled from the environment, especially in the all-fibre format. The attractive side of this decoupling is the simplicity of maintenance (no need to align the cavity or keep the optical elements clean), but [...] Read more.
Fibre lasers are distinct in that their optical train is decoupled from the environment, especially in the all-fibre format. The attractive side of this decoupling is the simplicity of maintenance (no need to align the cavity or keep the optical elements clean), but the flip side of this is the difficulty one encounters when trying to control the output parameters. The components used in all-fibre laser cavities are usually different from those of free-space laser cavities and require new approaches to control. Essentially, an important task emerges, i.e., research and development of all-fibre laser components able to adjust their parameters (ideally by electronic means) in order to tune key parameters of the output radiation—wavelength, output power, and so on. The present review analyses the existing methods of control over the output parameters of mode-locked all-fibre lasers. It is further noted that a method relying on several independently pumped active media may be promising in this regard. Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
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33 pages, 681 KiB  
Review
Mathieu–Hill Equation Stability Analysis for Trapped Ions: Anharmonic Corrections for Nonlinear Electrodynamic Traps
by Bogdan M. Mihalcea
Photonics 2024, 11(6), 551; https://doi.org/10.3390/photonics11060551 - 11 Jun 2024
Viewed by 619
Abstract
The stability properties of the Hill equation are discussed, especially those of the Mathieu equation that characterize ion motion in electrodynamic traps. The solutions of the Mathieu-Hill equation for a trapped ion are characterized by employing the Floquet theory and Hill’s method solution, [...] Read more.
The stability properties of the Hill equation are discussed, especially those of the Mathieu equation that characterize ion motion in electrodynamic traps. The solutions of the Mathieu-Hill equation for a trapped ion are characterized by employing the Floquet theory and Hill’s method solution, which yields an infinite system of linear and homogeneous equations whose coefficients are recursively determined. Stability is discussed for parameters a and q that are real. Characteristic curves are introduced naturally by the Sturm–Liouville problem for the well-known even and odd Mathieu equations cem(z,q) and sem(z,q). In the case of a Paul trap, the stable solution corresponds to a superposition of harmonic motions. The maximum amplitude of stable oscillations for ideal conditions (taken into consideration) is derived. We illustrate the stability diagram for a combined (Paul and Penning) trap and represent the frontiers of the stability domains for both axial and radial motion, where the former is described by the canonical Mathieu equation. Anharmonic corrections for nonlinear Paul traps are discussed within the frame of perturbation theory, while the frontiers of the modified stability domains are determined as a function of the chosen perturbation parameter and we demonstrate they are shifted towards negative values of the a parameter. The applications of the results include but are not restricted to 2D and 3D ion traps used for different applications such as mass spectrometry (including nanoparticles), high resolution atomic spectroscopy and quantum engineering applications, among which we mention optical atomic clocks and quantum frequency metrology. Full article
(This article belongs to the Special Issue Advances in Quantum Technologies Based on Trapped Charged Particles)
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16 pages, 6620 KiB  
Article
Long-Term Stability Test for Femtosecond Laser-Irradiated SnO2-Nanowire Gas Sensor for C7H8 Gas Sensing
by Sanghoon Ahn, Kang Woo Chun and Changkyoo Park
Photonics 2024, 11(6), 550; https://doi.org/10.3390/photonics11060550 - 11 Jun 2024
Viewed by 260
Abstract
In this study, femtosecond (FS) laser irradiation with different laser energy densities of 138, 276, and 414 mJ/cm2 is applied to SnO2-nanowire (NW) gas sensors, and the effect of the FS laser irradiation on the gas sensor response toward toluene [...] Read more.
In this study, femtosecond (FS) laser irradiation with different laser energy densities of 138, 276, and 414 mJ/cm2 is applied to SnO2-nanowire (NW) gas sensors, and the effect of the FS laser irradiation on the gas sensor response toward toluene (C7H8) gas is investigated. The FS laser irradiation causes oxygen deficiency in the SnO2 NWs and forms SnO and SnOx. Moreover, an embossing surface with multiple nano-sized bumps is created on the SnO2 NW surface because of the FS laser irradiation. The FS laser-irradiated SnO2-NW gas sensor exhibits superior sensing performance compared with the pristine SnO2-NW gas sensor. Moreover, the FS laser energy density significantly affects gas-sensing performance, and the highest sensor response is achieved by the gas sensor irradiated at 138 mJ/cm2. The long-term stability test of the laser-irradiated SnO2-NW gas sensor is performed by comparing fresh and 6-month-old gas sensors in different gas concentrations and relative humidity levels. Comparable gas-sensing behaviors are examined between the fresh and 6-month-old gas sensor, and this verifies the robustness of the laser-irradiated SnO2-NW gas sensor. Full article
(This article belongs to the Special Issue Advances in Ultrafast Laser Science and Applications)
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14 pages, 4293 KiB  
Article
A Highly Sensitive Plasmonic Graphene-Based Structure for Deoxyribonucleic Acid Detection
by Zohre Salehnezhad, Mohammad Soroosh and Haraprasad Mondal
Photonics 2024, 11(6), 549; https://doi.org/10.3390/photonics11060549 - 9 Jun 2024
Viewed by 513
Abstract
In this study, a Kretschmann structure with a hybrid layer of graphene–WS2 is designed to develop a sensitive biosensor for deoxyribonucleic acid detection. The biosensor incorporates a 45 nm gold layer as the active layer and a thin film of chrome as [...] Read more.
In this study, a Kretschmann structure with a hybrid layer of graphene–WS2 is designed to develop a sensitive biosensor for deoxyribonucleic acid detection. The biosensor incorporates a 45 nm gold layer as the active layer and a thin film of chrome as the adhesive layer. Through the optimization of the graphene and WS2 layers, combined with the implementation of a silicon layer, we can enhance the nano-sensor’s sensitivity. The thin silicon layer acts as a protective barrier for the metal, while also increasing the volume of interaction. Consequently, by adjusting the thickness of the active metal and adding a silicon layer, we achieve higher sensitivity and a lower full width at half maximum, leading to sensitivity of 333.33°/RIU. The designed structure is analyzed using numerical techniques and the finite difference time domain method, allowing us to obtain the optical characteristics of the surface plasmon polariton sensor. Various parameters are calculated and evaluated to determine the optimal conditions for the sensor. Furthermore, the total size of the sensor is 2.228 µm2. Full article
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8 pages, 3164 KiB  
Article
Temporal Analysis of Speckle Images in Full-Field Interferometric and Camera-Based Optical Dynamic Measurement
by Guojun Bai, Yuchen Wei, Bing Chen and Yu Fu
Photonics 2024, 11(6), 548; https://doi.org/10.3390/photonics11060548 - 8 Jun 2024
Viewed by 418
Abstract
Vibration measurement is crucial in fields like aviation, aerospace, and automotive engineering, which are trending towards larger, lighter, and more complex structures with increasingly complicated dynamics. Consequently, measuring a structure’s dynamic characteristics has gained heightened importance. Among non-contact approaches, those based on high-speed [...] Read more.
Vibration measurement is crucial in fields like aviation, aerospace, and automotive engineering, which are trending towards larger, lighter, and more complex structures with increasingly complicated dynamics. Consequently, measuring a structure’s dynamic characteristics has gained heightened importance. Among non-contact approaches, those based on high-speed cameras combined with laser interferometry or computational imaging have gained widespread attention. These techniques yield sequences of images that form a three-dimensional space-time data set. Effectively processing these data is a prerequisite for accurately extracting dynamic deformation information. This paper presents two examples to illustrate the significant advantages of signal processing along the time axis in dynamic interferometric and digital speckle-image-based dynamic measurements. The results show that the temporal process effectively minimizes speckle and electronic noise in the spatial domain and dramatically increases measurement resolutions. Full article
(This article belongs to the Special Issue Recent Advances in 3D Optical Measurement)
8 pages, 1987 KiB  
Article
Low-Power-Consumption and Broadband 16-Channel Variable Optical Attenuator Array Based on Polymer/Silica Hybrid Waveguide
by Shengyuan Zhang, Yuexin Yin, Zihao Wang, Yafan Li, Yuan Zhang, Mengke Yao, Daming Zhang and Ye Li
Photonics 2024, 11(6), 547; https://doi.org/10.3390/photonics11060547 - 8 Jun 2024
Viewed by 461
Abstract
A variable optical attenuator (VOA) is a crucial component for optical communication, especially for a variable multiplexer (VMUX) and reconfigurable optical add-drop multiplexer (ROADM). With the capacity increasing dramatically, a large-port-count and low-power-consumption VOA array is urgent for an on-chip system. In this [...] Read more.
A variable optical attenuator (VOA) is a crucial component for optical communication, especially for a variable multiplexer (VMUX) and reconfigurable optical add-drop multiplexer (ROADM). With the capacity increasing dramatically, a large-port-count and low-power-consumption VOA array is urgent for an on-chip system. In this paper, we experimentally demonstrate a 16-channel VOA array based on a polymer/silica hybrid waveguide. The proposed array is able to work over C and L bands. The VOA array shows an average attenuation larger than 14.38 dB with a low power consumption of 15.53 mW. The low power consumption makes it possible to integrate silica-based passive devices with a large port count on-chip. Full article
(This article belongs to the Special Issue Progress in Integrated Photonics and Future Prospects)
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17 pages, 5484 KiB  
Article
Comparison of Lifetime-Based Pressure-Sensitive Paint Measurements in a Wind Tunnel Using Model Pitch–Traverse and Pitch–Pause Modes
by Christian Klein, Daisuke Yorita and Ulrich Henne
Photonics 2024, 11(6), 546; https://doi.org/10.3390/photonics11060546 - 7 Jun 2024
Viewed by 372
Abstract
In order to improve the data productivity of a wind tunnel test, the model under investigation in the wind tunnel is moved continuously with a predetermined constant angular speed in the so-called pitch–traverse mode. Alternatively, the wind tunnel model can be moved in [...] Read more.
In order to improve the data productivity of a wind tunnel test, the model under investigation in the wind tunnel is moved continuously with a predetermined constant angular speed in the so-called pitch–traverse mode. Alternatively, the wind tunnel model can be moved in the so-called pitch–pause mode, in which it keeps its position for a certain (measurement) time at a fixed pitch position, after which it is moved to the next pitch position. The latter procedure is more time-consuming, so, for the same time interval, the number of measured data points taken in the pitch–pause mode is less than that for the pitch–traverse mode. Since wind tunnel test time can be quite expensive, in most wind tunnel tests where only conventional forces and pressures are recorded with conventional measuring systems, the wind tunnel model is moved in the pitch–traverse mode in order to obtain as much aerodynamic data as possible during the tunnel runtime. The application of the Pressure-Sensitive Paint (PSP) technique has been widely used in wind tunnel testing for the purpose of providing pressure data on wind tunnel models with high spatial resolution. The lifetime-based PSP method has several advantages over the intensity-based method since it often has higher accuracy. Up until now, the lifetime-based PSP technique has mainly been used for wind tunnel testing, where the test model has been moved to the pitch–pause mode. The traditional lifetime method using on-chip accumulation requires multiple (~1000) excitation light pulses to accumulate enough luminescence (fluorescence or phosphorescence) photons on the camera sensor to provide acceptable signal-to-noise ratios and, therefore, it may seem to be not compatible with a continuously moving wind tunnel model. Nevertheless, the present study verifies the application of lifetime-based PSP utilizing on-chip accumulation with a continuously moving wind tunnel model which would make the entire PSP data acquisition compatible with that of the conventional measurements (forces and pressures), as mentioned above. In this paper, the applicability of the lifetime-based PSP technique to a continuously moving wind tunnel model (in pitch–traverse mode) is investigated with the help of measurements in the transonic wind tunnel in Göttingen (TWG). For this investigation, PSP was applied on the delta-wing model DLR-F22, which is to be tested in TWG. The pressure distribution on the wind tunnel model was measured using the PSP lifetime method for both model movement modes (pitch–pause and pitch–traverse mode) so that the corresponding PSP results could be directly compared with each other. In addition, an error analysis of the PSP results was carried out and compared with the conventional pressure measurement results, hence providing an assessment of the accuracy of the PSP results; finally, a recommendation for future PSP measurements could be given. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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18 pages, 24888 KiB  
Article
Miniaturized Multi-Platform Free-Space Laser-Communication Terminals for Beyond-5G Networks and Space Applications
by Alberto Carrasco-Casado, Koichi Shiratama, Dimitar Kolev, Fumie Ono, Hiroyuki Tsuji and Morio Toyoshima
Photonics 2024, 11(6), 545; https://doi.org/10.3390/photonics11060545 - 7 Jun 2024
Viewed by 409
Abstract
Beyond-5G (B5G) technology plays a pivotal role in the next generation of communication infrastructure to support the future Society 5.0, a concept introduced in the 5th Basic Plan for Science and Technology by the Japanese Cabinet to define the long-term growth strategy for [...] Read more.
Beyond-5G (B5G) technology plays a pivotal role in the next generation of communication infrastructure to support the future Society 5.0, a concept introduced in the 5th Basic Plan for Science and Technology by the Japanese Cabinet to define the long-term growth strategy for reconciling economic development with the resolution of social issues through the promotion of science and technologies. Free-space laser communication is a key element in boosting the data transmission capabilities required for B5G applications. The NICT will complete in 2024 the first fully functional prototypes of a series of miniaturized laser-communication terminals for multiple platforms. These terminals are designed to adapt to a wide range of requirements to address scenarios where laser communications can offer a competitive, enhanced solution compared to existing technologies. This paper provides an overview of these terminals’ capabilities and the plans for their functional validation, as well as preliminary data from the first full-system tests. A number of innovations integrated into the terminals are introduced, such as the manufacture of the smallest miniaturized EDFA with integrated HPA and LNA and full space qualification to date, the first-ever integration of a beam-divergence control system in a practical communication terminal, the development of the most compact Tbit/s-class modem prototype documented in the literature, and the smallest gimbal design integrated in a lasercom terminal. Furthermore, this paper outlines the mid-term plans for demonstration in the most significant realistic scenarios, emphasizing the use of High-Altitude Platform Stations (HAPSs) and ultra-small satellites. Full article
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11 pages, 3451 KiB  
Article
High-Performance Terahertz Coherent Perfect Absorption with Asymmetric Graphene Metasurface
by Jintao Chen, Lujun Hong, Jiangtao Lei, Yun Shen, Xiaohua Deng, Jing Chen and Tianjing Guo
Photonics 2024, 11(6), 544; https://doi.org/10.3390/photonics11060544 - 7 Jun 2024
Viewed by 310
Abstract
In this work, we introduce a novel coherent perfect absorber, accentuating its novelty by emphasizing the broad bandwidth, reduced thickness, tunable property, and straightforward design achieved through the use of an asymmetric graphene metasurface. This design incorporates both square and circular graphene patches [...] Read more.
In this work, we introduce a novel coherent perfect absorber, accentuating its novelty by emphasizing the broad bandwidth, reduced thickness, tunable property, and straightforward design achieved through the use of an asymmetric graphene metasurface. This design incorporates both square and circular graphene patches arranged on either side of a silicon substrate. With an optimized structural design, this absorber consistently captures over 90% of incoming waves across the frequency range of 1.65 to 4.49 THz, with a graphene Fermi level of 0.8 eV, and the whole device measures just 1.5 um thick. This makes our absorber significantly more effective and compact than previous designs. The absorber’s effectiveness can be significantly enhanced by combining the metasurface’s geometric design with the graphene Fermi level. It is anticipated that this ultrathin, wideband coherent perfect absorption device will play a crucial role in emerging on-chip THz communication technologies, including light modulators, photodetectors, and so on. Full article
(This article belongs to the Special Issue Advanced Lasers and Their Applications II)
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13 pages, 2843 KiB  
Article
Asymmetrical Three-Dimensional Conformal Imaging Lens
by Desen Gong, Yixiao Ge, Wen Xiao and Huanyang Chen
Photonics 2024, 11(6), 543; https://doi.org/10.3390/photonics11060543 - 7 Jun 2024
Viewed by 370
Abstract
Absolute instrument refers to a media that can make light rays to propagate in a closed orbit and perform imaging and self-imaging. In the past few decades, traditional investigations into absolute instrument have been centered on the two-dimensional plane and rotational symmetry situations, [...] Read more.
Absolute instrument refers to a media that can make light rays to propagate in a closed orbit and perform imaging and self-imaging. In the past few decades, traditional investigations into absolute instrument have been centered on the two-dimensional plane and rotational symmetry situations, and have paid less attention to three-dimensional counterparts. In this article, we design two types of three-dimensional non-spherically symmetric absolute instruments based on conformal inverse transformation, which originated from the three-dimensional Luneburg lens and Lissajous lens. We carry out ray tracing on the optical performance of these new lenses and analyze the imaging laws. Our work enlarges the family of absolute instruments from two dimensions to three dimensions and symmetry to asymmetry, which may allow for imaging applications in optical waves. Full article
(This article belongs to the Special Issue Recent Advances in Optical Metamaterials and Metasurfaces)
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