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Photonics, Volume 9, Issue 8 (August 2022) – 88 articles

Cover Story (view full-size image): Butterfly wings with hierarchically organized structures from nanometer to centimeter scales were tested as substrates for plasmonic Au and Ag/Au nanoparticles with potential application in photocatalysis. Au and Ag/Au alloy nanoparticles form a new, hybrid nanostructure with the chitinous photonic nanoarchitecture, modifying the structural color of the butterfly wings. The optical properties of the new hybrid photonic nanoarchitectures are different from both components. The butterfly wings with structural color offer cheap, highly specific surface substrates for plasmonic nanoparticles and a way of engineering the properties of the hybrid nanoarchitectures. The butterflies used were reared in a lab experiment, where one breeding pair may have as many as 600–700 descendants. View this paper
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20 pages, 50724 KiB  
Article
Green Synthesis and Characterization of ZnO Nanoparticles by Using Thyme Plant Leaf Extract
by Shayma Tahsin Karam and Ahmed Fattah Abdulrahman
Photonics 2022, 9(8), 594; https://doi.org/10.3390/photonics9080594 - 22 Aug 2022
Cited by 41 | Viewed by 6372
Abstract
Zinc oxide (ZnO) nanoparticles (NPs) were fabricated by using leaves extracted from the thyme plant by employing a green method. The influence of several calcination (annealing) temperatures on the characteristic properties of fabricated ZnO NPs and the optimum calcination temperature for growing ZnO [...] Read more.
Zinc oxide (ZnO) nanoparticles (NPs) were fabricated by using leaves extracted from the thyme plant by employing a green method. The influence of several calcination (annealing) temperatures on the characteristic properties of fabricated ZnO NPs and the optimum calcination temperature for growing ZnO NPs were studied and reported. The studied calcination temperatures were 150 °C, 250 °C, 350 °C, and 450 °C. Different characterization techniques were used to study and examine the properties of biosynthesized ZnO NPs by using thyme plant leaf extract. The results of each UV-Vis analysis and FTIR spectrum of the leaf extract of the thyme plant confirmed and suggested that the selected leaf extract of thyme is a practicable choice for green synthesis of ZnO NPs. The investigated UV-Vis spectra of plant leaf extract displayed two strong absorption peaks at 266 nm and 313 nm at ambient temperature. The results of FESEM images showed that the calcination temperature has a significant and large effect on the morphology, size, shape, and orientation of ZnO NPs, which have a spherical shape with an average size in the range of 39.4–51.86 nm. In addition, the XRD results confirm that the ZnO NPs formed are pure ZnO with wurtzite hexagonal structure with particle size along the (002) peak in the range of 35.20–243.3 nm. The results of UV-Vis of ZnO NPs displayed a strong peak for all ZnO NPs produced at different calcination temperatures, a high absorbance in the UV region below 400 nm, and a low absorbance rate in the visible range. The obtained energy band gap (Eg) was in the range of 2.645–2.7 eV. In addition, the results of the FTIR spectra of ZnO NPs at different calcination temperatures revealed there was no discernible peak in the monitoring range, which indicated the purity of the ZnO nanoparticles generated via using thyme leaf extract. In addition, from all obtained results of the fabricated ZnO NPs, the ZnO NPs synthesized at the calcination temperature of 450 °C showed a high quality and improvement compared to the ZnO NPs synthesized at other calcination temperatures. Full article
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13 pages, 10057 KiB  
Article
Identifying Collector Channel Orifices In Vivo with Phase-Sensitive Optical Coherence Tomography: A Preliminary Study
by Guangxu Li
Photonics 2022, 9(8), 593; https://doi.org/10.3390/photonics9080593 - 20 Aug 2022
Viewed by 1888
Abstract
Collector channels are openings located in the trabecular meshwork (TM) of the human eye that function as conduits, connecting the anterior chamber to the episcleral veins. Identifying the positions of collector channel orifices (CCOs) is essential for positioning implants in microinvasive canal-based glaucoma [...] Read more.
Collector channels are openings located in the trabecular meshwork (TM) of the human eye that function as conduits, connecting the anterior chamber to the episcleral veins. Identifying the positions of collector channel orifices (CCOs) is essential for positioning implants in microinvasive canal-based glaucoma surgery, which is still not possible in vivo currently. Considerable evidence indicates that aqueous outflow becomes more active near the CCOs. Because the TM movement regulates the aqueous outflow, identification of the TM motion signal has the potential to locate the CCOs. Phase-sensitive optical coherence tomography (PhS-OCT) is an effective tool for the instantaneous detection of TM motion in vivo with sensitivity at the nanometer scale. However, the downside of this method is that phase measurement is prone to mix noises that negatively distinguish between biomedical signals. The TM motion was considered initially to be set up by the cardiac pulse. In this paper, a signal quality index related to blood pressure monitoring was applied to assess the validity of the TM motion signal. Measurements were carried out on two pairs of healthy human eyes. Quantitative measurements of the TM motion signal region such as size and frequency were recorded as the judgment indicator for CCOs. These results demonstrate that the PhS-OCT is a valuable tool capable of revealing the aqueous outflow pathway in vivo, offering a novel alternative to optimize glaucoma surgery. Full article
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11 pages, 6770 KiB  
Article
Measuring of Transverse Energy Flows in a Focus of an Aluminum Lens
by Elena Kozlova, Sergey Stafeev, Sergey Fomchenkov, Vladimir Podlipnov, Alexandra Savelyeva and Victor Kotlyar
Photonics 2022, 9(8), 592; https://doi.org/10.3390/photonics9080592 - 20 Aug 2022
Cited by 3 | Viewed by 1260
Abstract
In this study, we theoretically and experimentally investigate the propagation of a second-order cylindrical vector beam through an aluminum lens which forms a tight focus at the distance of the wavelength. Simulation by the finite-difference time-domain method and the Richards–Wolf formulae produces light [...] Read more.
In this study, we theoretically and experimentally investigate the propagation of a second-order cylindrical vector beam through an aluminum lens which forms a tight focus at the distance of the wavelength. Simulation by the finite-difference time-domain method and the Richards–Wolf formulae produces light field distributions which coincide with experimental measurements provided with scanning near-field optical microscopy. We demonstrate that a pyramidal metallized cantilever with a hole is more sensitive to the transversal component of intensity than to the full intensity or to the Umov–Poynting vector in areas of reverse energy flow. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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10 pages, 1395 KiB  
Article
Biophotonic Effects of Low-Level Laser Therapy at Different Wavelengths for Potential Wound Healing
by Tzu-Sen Yang, Le-Thanh-Hang Nguyen, Yu-Cheng Hsiao, Li-Chern Pan and Cheng-Jen Chang
Photonics 2022, 9(8), 591; https://doi.org/10.3390/photonics9080591 - 19 Aug 2022
Cited by 6 | Viewed by 2979
Abstract
Our objective was to assess the effect of low-level laser therapy (LLLT) administered using a diode laser on the growth processes of human fibroblast cells involved in wound healing. Initially, studies were conducted using a diode laser at wavelengths of 633, 520, and [...] Read more.
Our objective was to assess the effect of low-level laser therapy (LLLT) administered using a diode laser on the growth processes of human fibroblast cells involved in wound healing. Initially, studies were conducted using a diode laser at wavelengths of 633, 520, and 450 nm with an irradiance of 3 mW/cm2. The distance between the light source and culture plate was 3 cm. The mechanism(s) of action of the diode laser illumination on human fibroblast cells were studied by examining different wavelengths to determine the relevant light parameters for optimal treatment. In addition, the percentages of fibroblast-mediated procollagen and matrix metallopeptidase (MMP)-1, -2, and -9 production were compared. In the clinical study, the changes in basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and fibroblast collagen production were assessed in 60 patients with complicated wounds who received LLLT (633 nm). No statistically significant difference was observed between red light versus green and blue light in the viability analysis. In addition, the effects of LLLT on the cell cultures of fibroblast cells in vitro demonstrated a decrease in the relative expression of MMP-1, -2, and -9 while using light with a wavelength of 633 nm. In the clinical study, 633 nm diode laser LLLT at 2–8 J/cm2 was administered to 60 patients with complicated wounds; all patients showed increased levels of bFGF and VEGF and the occurrence of collagen synthesis. Our studies demonstrated that LLLT might affect fibroblast cell growth processes involved in wound healing. Full article
(This article belongs to the Topic Biomedical Photonics)
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9 pages, 2766 KiB  
Communication
Extreme Narrowing of the Distributed Feedback Fiber Laser Linewidth Due to the Rayleigh Backscattering in a Single-Mode Fiber: Model and Experimental Test
by Mikhail I. Skvortsov, Sofia R. Abdullina, Evgeny V. Podivilov, Alexander A. Vlasov, Danil R. Kharasov, Edgard A. Fomiryakov, Sergey P. Nikitin, Vladimir N. Treshchikov and Sergey A. Babin
Photonics 2022, 9(8), 590; https://doi.org/10.3390/photonics9080590 - 19 Aug 2022
Cited by 11 | Viewed by 1951
Abstract
We present our theoretical model and experimental results on the extreme linewidth narrowing of an erbium-doped fiber distributed feedback (DFB) laser due to an additional random DFB via Rayleigh backscattering in a long single-mode fiber connected to the laser. The relative narrowing of [...] Read more.
We present our theoretical model and experimental results on the extreme linewidth narrowing of an erbium-doped fiber distributed feedback (DFB) laser due to an additional random DFB via Rayleigh backscattering in a long single-mode fiber connected to the laser. The relative narrowing of instantaneous (<1 μs) linewidth in such a hybrid cavity configuration predicted by the theoretical model may exceed six orders of magnitude, whereas the linewidth estimated from the phase noise measurements narrows by four orders of magnitude from 15 Hz to 10–3 Hz in the hybrid configuration, with the lower limit defined by the background electrical noise. Significant narrowing was also observed for the long-term ≥10 μs) linewidth directly measured by the self-delay heterodyne technique: the values for the DFB laser and hybrid configuration amount to 6 kHz and 160 Hz, respectively. Full article
(This article belongs to the Special Issue Rare Earth Doped Fiber Lasers)
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9 pages, 1756 KiB  
Article
High-Power, Narrow-Linewidth Distributed-Feedback Quantum-Cascade Laser for Molecular Spectroscopy
by Mathieu Bertrand, Aleksandr Shlykov, Mehran Shahmohamadi, Mattias Beck, Stefan Willitsch and Jérôme Faist
Photonics 2022, 9(8), 589; https://doi.org/10.3390/photonics9080589 - 19 Aug 2022
Cited by 3 | Viewed by 2158
Abstract
Quantum cascade lasers are versatile light sources in the mid-infrared range for molecular spectroscopy which find a wide range of applications from high-resolution studies to sensing. While devices with either high power or narrow spectral linewidth have previously been reported, there is still [...] Read more.
Quantum cascade lasers are versatile light sources in the mid-infrared range for molecular spectroscopy which find a wide range of applications from high-resolution studies to sensing. While devices with either high power or narrow spectral linewidth have previously been reported, there is still a lack of sources combining both of these characteristics which are particularly important for precision measurements of weak spectroscopic transitions. In this article, we describe and characterize a novel master-oscillator power-amplifier distributed-feedback quantum cascade laser designed to fill this gap. At an output power of 300 mW, the device features a free-running linewidth of 1.3 MHz, measured with a frequency discriminator technique, at an emission wavenumber of 2185 cm1. This linewidth is sufficiently narrow to enable a further reduction by a tight lock to a high-Q oscillator. Full article
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9 pages, 2140 KiB  
Article
A Graphene/Gold-Coated Surface Plasmon Sensor for Sodium Nitrate Detection
by H. A Zain, M. Batumalay, Z. Harith, H. R. A. Rahim and S. W. Harun
Photonics 2022, 9(8), 588; https://doi.org/10.3390/photonics9080588 - 19 Aug 2022
Cited by 1 | Viewed by 1286
Abstract
A sodium nitrate sensor with graphene/gold coating is presented in this paper. A Kretschmann setup with angle interrogation was used to detect sodium nitrate in the range of 0–15%. Using a graphene coating on top of the 50 nm gold layer showed an [...] Read more.
A sodium nitrate sensor with graphene/gold coating is presented in this paper. A Kretschmann setup with angle interrogation was used to detect sodium nitrate in the range of 0–15%. Using a graphene coating on top of the 50 nm gold layer showed an improvement in the sensitivity of the sensor. The gold-coated setups had a sensitivity of 0.198°/%. In contrast, the graphene/gold-coated samples showed a sensitivity of 0.244°/% due to the charge transfer between the graphene and the gold and the resulting excited solid electric field. The graphene/gold-coated sensor showed good stability with time in the temperature range of 19–34 °C. This shows that this setup may be beneficial in detecting sodium nitrate. Full article
(This article belongs to the Special Issue Optical Sensing)
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13 pages, 915 KiB  
Article
A Surface Plasmon–Polariton in a Symmetric Dielectric Waveguide with Active Graphene Plates
by Dmitry A. Evseev, Svetlana V. Eliseeva, Dmitry I. Sementsov and Anatolij M. Shutyi
Photonics 2022, 9(8), 587; https://doi.org/10.3390/photonics9080587 - 19 Aug 2022
Cited by 8 | Viewed by 1317
Abstract
A theoretical study of the plasmon modes’ characteristics is carried out in a structure consisting of two active graphene layers separated by a dielectric barrier layer. A general dispersion relation is obtained, the numerical analysis of which reveals the possibility of controlling the [...] Read more.
A theoretical study of the plasmon modes’ characteristics is carried out in a structure consisting of two active graphene layers separated by a dielectric barrier layer. A general dispersion relation is obtained, the numerical analysis of which reveals the possibility of controlling the parameters of amplified surface modes in the region of graphene negative conductivity. In particular, their dispersion is controlled by changing the chemical potential of the graphene layers. For antisymmetric plasmons, their dependence on the barrier layer parameters was revealed. An increase in the chemical potential makes it possible to expand the region of existence of the amplified plasmons, which is accompanied not only by an increase in the amplification coefficient but also by a shift to the region of higher frequencies of the amplified modes. For the first time, modal bistability was also demonstrated in a limited frequency range for antisymmetric plasmons, due to the appearance of additional modes, in which the phase velocity decreases sharply near the cutoff, and the group velocities of the modes entering the bistability turn out to be opposite in sign. The frequency dependences of the real and imaginary parts of the plasmon propagation constant are analyzed, the distributions of wave fields in the structure are plotted, and the frequency dependence of the depth of the plasmon–polariton is given. Full article
(This article belongs to the Special Issue Terahertz (THz) Science in Advanced Materials, Devices and Systems)
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13 pages, 2913 KiB  
Article
Specific Phase Modulation with Dynamic Variable Spectral Width of Nanosecond Optical Pulse in High-Power Lasers
by Xinlei Qian, Xiaochao Wang, Shouying Xu, Zhuli Xiao, Yue Wang, Shenlei Zhou and Wei Fan
Photonics 2022, 9(8), 586; https://doi.org/10.3390/photonics9080586 - 18 Aug 2022
Viewed by 1471
Abstract
High-power laser pulse transmitted by phase modulation with certain spectrum distribution can suppress the buildup of transverse stimulated Brillouin scattering (TSBS) in large aperture laser optics and smooth the speckle pattern illuminating the target by spectral smoothing dispersion (SSD). In this paper, based [...] Read more.
High-power laser pulse transmitted by phase modulation with certain spectrum distribution can suppress the buildup of transverse stimulated Brillouin scattering (TSBS) in large aperture laser optics and smooth the speckle pattern illuminating the target by spectral smoothing dispersion (SSD). In this paper, based on the requirements of the double-cone ignition scheme including simultaneously realizing that the focal spot is variable at different times in size and the spatial intensity distribution is uniform, we propose a novel phase modulation technology with a rapid variable modulation index in the nanosecond scale instead of utilizing conventional constant amplitude sinusoidal curve. The relevant simulation results indicate that the proposed technology can realize the dynamic nanosecond spectral distribution and the trend correlates with the variety of modulation index. Particularly, we indirectly measure this rapid changeable spectral distribution based on the mapping relationship between frequency and time domain. We believe that the new technology is expected to meet the requirements of SSD and the dynamic focus simultaneously. Full article
(This article belongs to the Special Issue High Power Laser: Theory and Applications)
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10 pages, 410 KiB  
Article
Nonreciprocity Steered with a Spinning Resonator
by Xiao Shang, Hong Xie, Gongwei Lin and Xiumin Lin
Photonics 2022, 9(8), 585; https://doi.org/10.3390/photonics9080585 - 18 Aug 2022
Cited by 2 | Viewed by 1600
Abstract
An approach is presented to study the controllable nonreciprocal transmission in a spinning resonator. It has been demonstrated in optomechanics that an optical signal field can only be affected when it propagates in the same direction as the driving field. We show that [...] Read more.
An approach is presented to study the controllable nonreciprocal transmission in a spinning resonator. It has been demonstrated in optomechanics that an optical signal field can only be affected when it propagates in the same direction as the driving field. We show that such an optomechanically induced nonreciprocity can be controlled by rotating the resonator, which introduces a frequency shift with different signs for clockwise and counterclockwise optical fields in the resonator. In our scheme, the transmission probabilities of the clockwise and counterclockwise input signal fields can be reversed by tuning the rotation velocity of the resonator. By studying the transmission spectra of the signal field, we also reveal that the nonreciprocity response can be realized in the spinning resonators in the absence of optomechanical coupling, which extends its utility. Full article
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19 pages, 3184 KiB  
Article
Quantitative Evaluation of the Phase Function Effects on Light Scattering and Radiative Transfer in Dispersed Systems
by Lanxin Ma, Lechuan Hu, Chengwei Jia, Chengchao Wang and Linhua Liu
Photonics 2022, 9(8), 584; https://doi.org/10.3390/photonics9080584 - 18 Aug 2022
Cited by 2 | Viewed by 1410
Abstract
The light scattering properties of particles play important roles in radiative transfer in many dispersed systems, such as turbid atmosphere, ocean water, nanofluids, composite coatings and so on. As one of the scattering property parameters, the scattering phase functions of particles are strongly [...] Read more.
The light scattering properties of particles play important roles in radiative transfer in many dispersed systems, such as turbid atmosphere, ocean water, nanofluids, composite coatings and so on. As one of the scattering property parameters, the scattering phase functions of particles are strongly dependent on the particle size, size distribution, and morphology, as well as on the complex refractive indices of the particles and surrounding media. For the sake of simplicity, the empirical phase function models are widely used in many practical applications. In this work, we focus on the radiative transfer problem in dispersed systems composed of spherical particles, and give quantitative analyses of the impact of scattering phase functions on the radiative transfer process. We fit the scattering phase functions of four different types of practical dispersed systems using four previously proposed empirical phase function models, including the Henyey–Greenstein (HG) model, Cornette Shanks (CS) model, Reynold and McCormick (RM) model and two-term Reynolds–McCormick (TTRM) model. By comparing the radiative transfer characteristics (i.e., hemispherical reflectance, hemispherical transmittance and total absorptance) of dispersed layers calculated using the Monte Carlo method, the relative errors caused by using the empirical phase functions are systematically investigated. The results demonstrate that the HG, CS and RM models cause obvious errors in the calculation of hemispherical reflectance in many cases. Meanwhile, the induced errors show no obvious regularity, but are related to the particle size and layer optical thickness. Due to the good fitting effect in both forward and backward directions, the TTRM model provides significantly higher performances in fitting the phase functions of all considered cases than the widely used single-term parametrizations. Moreover, for different particle sizes and layer optical thicknesses, the induced errors of the TTRM model in radiative transfer characteristics are very small, especially for the case of polydisperse particles. Our results can be used to guide the design, analysis and optimization of dispersed systems in practical optics and photonics applications. Full article
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12 pages, 2671 KiB  
Article
Implementation of Photonic Phase Gate and Squeezed States via a Two-Level Atom and Bimodal Cavity
by Shiqing Tang, Xi Jiang, Xinwen Wang and Xingdong Zhao
Photonics 2022, 9(8), 583; https://doi.org/10.3390/photonics9080583 - 18 Aug 2022
Viewed by 1524
Abstract
We propose a theoretical model for realizing a photonic two-qubit phase gate in cavity QED using a one-step process. The fidelity and probability of success of the conditional quantum phase gate is very high in the presence of cavity decay. Our scheme only [...] Read more.
We propose a theoretical model for realizing a photonic two-qubit phase gate in cavity QED using a one-step process. The fidelity and probability of success of the conditional quantum phase gate is very high in the presence of cavity decay. Our scheme only employs one two-level atom, and thus is much simpler than other schemes involving multi-level atoms. This proposal can also be applied to generate two-mode squeezed states; therefore, we give three examples, i.e., the two-mode squeezed vacuum state, two-mode squeezed odd coherent state, and two-mode squeezed even coherent state, to estimate the variance of Duan’s criterion when taking into account cavity decay. It is shown that the variance is smaller than 2 for the three squeezed states in most cases. Furthermore, we utilize logarithmic negativity to measure the entanglement, and find that these squeezed states have very high degrees of entanglement. Full article
(This article belongs to the Special Issue Quantum Optics: Science and Applications)
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17 pages, 6944 KiB  
Article
Blind Restoration of Images Distorted by Atmospheric Turbulence Based on Deep Transfer Learning
by Yiming Guo, Xiaoqing Wu, Chun Qing, Changdong Su, Qike Yang and Zhiyuan Wang
Photonics 2022, 9(8), 582; https://doi.org/10.3390/photonics9080582 - 18 Aug 2022
Cited by 4 | Viewed by 1721
Abstract
Removing space-time varying blur and geometric distortions simultaneously from an image is a challenging task. Recent methods (including physical-based methods or learning-based methods) commonly default the turbulence-degraded operator as a fixed convolution operator. Obviously, the assumption does not hold in practice. According to [...] Read more.
Removing space-time varying blur and geometric distortions simultaneously from an image is a challenging task. Recent methods (including physical-based methods or learning-based methods) commonly default the turbulence-degraded operator as a fixed convolution operator. Obviously, the assumption does not hold in practice. According to the situation that the real turbulence distorted operator has double uncertainty in space and time dimensions, this paper reports a novel deep transfer learning (DTL) network framework to address this problem. Concretely, the training process of the proposed approach contains two stages. In the first stage, the GoPro Dataset was used to pre-train the Network D1 and freeze the bottom weight parameters of the model; in the second stage, a small amount of the Hot-Air Dataset was employed for finetuning the last two layers of the network. Furthermore, residual fast Fourier transform with convolution block (Res FFT-Conv Block) was introduced to integrate both low-frequency and high-frequency residual information. Subsequently, extensive experiments were carried out with multiple real-world degraded datasets by implementing the proposed method and four existing state-of-the-art methods. In contrast, the proposed method demonstrates a significant improvement over the four reported methods in terms of alleviating the blur and distortions, as well as improving the visual quality. Full article
(This article belongs to the Special Issue Artificial Intelligence and Machine Learning in Photonics)
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10 pages, 5098 KiB  
Article
Binary Computer-Generated Holograms by Simulated-Annealing Binary Search
by Jung-Ping Liu and Chen-Ming Tsai
Photonics 2022, 9(8), 581; https://doi.org/10.3390/photonics9080581 - 18 Aug 2022
Cited by 5 | Viewed by 1878
Abstract
The binary computer-generated hologram (BCGH) has attracted much attention recently because it can address the high-speed binary spatial light modulator (SLM), such as a digital micromirror device (DMD) SLM. In this paper, our concern is the development of an algorithm to produce high-quality [...] Read more.
The binary computer-generated hologram (BCGH) has attracted much attention recently because it can address the high-speed binary spatial light modulator (SLM), such as a digital micromirror device (DMD) SLM. In this paper, our concern is the development of an algorithm to produce high-quality BCGHs. In particular, simulated annealing (SA) is an efficient algorithm used to produce a phase-only computer-generated hologram. In the study of SA for the production of a BCGH, we found some inherent shortcomings of SA, and the quality of the produced BCGHs is limited. Accordingly, we have modified SA and propose the simulated-annealing binary search (SABS) algorithm. We have also proposed a method to quickly determine the parameters for SABS. In the comparison with SA, the mean square error of the SABS BCGHs decreases by 32% on average. Therefore, the SABS is a promising technique for a high-quality holographic display by DMD. Full article
(This article belongs to the Special Issue Computer Holography)
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16 pages, 7500 KiB  
Article
A Novel Design of Optical Switch Based on Guided Mode Resonances in Dielectric Photonic Crystal Structures
by Atiq Ur Rehman, Yousuf Khan, Muhammad Irfan, Muhammad A. Butt, Svetlana N. Khonina and Nikolay L. Kazanskiy
Photonics 2022, 9(8), 580; https://doi.org/10.3390/photonics9080580 - 17 Aug 2022
Cited by 7 | Viewed by 2353
Abstract
In this work, a novel idea of optical switch design based on guided mode resonance in the photonic crystal structure is numerically investigated. The designed switching device work on the principle of optical amplification and wavelength shift of data signal with the help [...] Read more.
In this work, a novel idea of optical switch design based on guided mode resonance in the photonic crystal structure is numerically investigated. The designed switching device work on the principle of optical amplification and wavelength shift of data signal with the help of a control signal. The data signal can be coupled into the waveguide using guided-mode resonance, whereas, a control signal is index-coupled into the waveguide to influence the data signal. The optical switching action is optimized by introducing a photonic crystal cavity and varying the number of photonic crystal elements, where the resonant wavelength, reflection peaks, linewidth, and quality factor of the data signal can be adjusted. The device is based on low refractive index contrast dielectric materials compatible with fiber optic communication and can operate in a near-infrared range of around 1.55 μm. The numerical simulations are carried out in an open source finite-difference time-domain-based software. An optical switching action is achieved with 7% amplification in the data signal at a central wavelength of 1.55 µm with a maximum shift of the wavelength of 0.001 µm. The proposed device can be easily implemented in cascade designs of programmable photonic and optical switching circuits. Full article
(This article belongs to the Special Issue Photonic Crystals: Physics and Devices)
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12 pages, 1828 KiB  
Communication
74.7% Efficient GaAs-Based Laser Power Converters at 808 nm at 150 K
by Simon Fafard and Denis P. Masson
Photonics 2022, 9(8), 579; https://doi.org/10.3390/photonics9080579 - 17 Aug 2022
Cited by 22 | Viewed by 3939
Abstract
High-efficiency multijunction laser power converters are demonstrated for low temperature applications with an optical input at 808 nm. The photovoltaic power converting III-V semiconductor devices are designed with GaAs absorbing layers, here with 5 thin subcells (PT5), connected by transparent tunnel junctions. Unprecedented [...] Read more.
High-efficiency multijunction laser power converters are demonstrated for low temperature applications with an optical input at 808 nm. The photovoltaic power converting III-V semiconductor devices are designed with GaAs absorbing layers, here with 5 thin subcells (PT5), connected by transparent tunnel junctions. Unprecedented conversion efficiencies of up to 74.7% are measured at temperatures around 150 K. At temperatures around 77 K, a remarkably low bandgap offset value of Woc = 71 mV is obtained at an optical input intensity of ~7 W/cm2. At 77 K, the PT5 retains an efficiency of 65% with up to 0.3 W of converted output power. Full article
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12 pages, 1871 KiB  
Article
Exciton Transfer Dynamics and Annihilation in Rubidium–Cesium-Alloyed, Quasi-Two-Dimensional Perovskite
by Lamiaa Abdelrazik, Vidmantas Jašinskas, Žydrūnas Podlipskas, Ramūnas Aleksiejūnas, Gintautas Tamulaitis, Vidmantas Gulbinas and Aurimas Vyšniauskas
Photonics 2022, 9(8), 578; https://doi.org/10.3390/photonics9080578 - 17 Aug 2022
Viewed by 2585
Abstract
Light-emitting diodes (LEDs) based on perovskite materials are a new group of devices that are currently undergoing rapid development. A significant fraction of these devices is based on quasi-2D perovskites fabricated with large organic cations. In this work, we describe the ultrafast scale [...] Read more.
Light-emitting diodes (LEDs) based on perovskite materials are a new group of devices that are currently undergoing rapid development. A significant fraction of these devices is based on quasi-2D perovskites fabricated with large organic cations. In this work, we describe the ultrafast scale dynamics in a quasi-2D PEA2(Rb0.6Cs0.4)2Pb3Br10 perovskite material with an excess of RbBr, which was previously used to fabricate blue-emitting perovskite LEDs. The results obtained using transient absorption spectroscopy are consistent with the assumption that the carrier dynamics in this material are dominated by excitons, most of which decay by exciton–exciton annihilation when high-intensity excitation is used. Furthermore, a slow energy transfer between different quasi-2D domains taking place within 50 ps was observed. The content of the RbBr did not show any strong influence on the observed dynamics. Our results show that the exciton–exciton annihilation proceeds much faster in thin (n = 2) quasi-2D domains than in thick (n ≥ 4) domains. This finding implies that perovskites with high-n, quasi-2D domains are preferable for efficient perovskite lasers and bright perovskite LEDs. Full article
(This article belongs to the Special Issue Organic and Hybrid Optoelectronic Materials and Devices)
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11 pages, 2730 KiB  
Article
Influence of Gain Saturation Effect on Transverse Mode Instability Considering Four-Wave Mixing
by Haobo Li, Liangjin Huang, Hanshuo Wu, Zhiyong Pan and Pu Zhou
Photonics 2022, 9(8), 577; https://doi.org/10.3390/photonics9080577 - 17 Aug 2022
Cited by 2 | Viewed by 1356
Abstract
Transverse mode instability (TMI) has been recognized as onse of the primary limiting factors for the average power scaling of high-brightness fiber lasers. In this work, a static model of the TMI effect based on stimulated thermal Rayleigh scattering (STRS) is established while [...] Read more.
Transverse mode instability (TMI) has been recognized as onse of the primary limiting factors for the average power scaling of high-brightness fiber lasers. In this work, a static model of the TMI effect based on stimulated thermal Rayleigh scattering (STRS) is established while considering the four-wave mixing (FWM) effect. The focus of the model is to theoretically investigate the TMI phenomenon and threshold power dominated by FWM. The gain saturation effect and fiber laser system parameters, such as seed power, pumping direction, and core numerical aperture, which have not been considered in the previous perturbation theory model, are also investigated. This work will enrich the perturbation theory model and extend its application scope in TMI mitigation strategies, providing guidance for understanding and suppressing TMI. Full article
(This article belongs to the Special Issue Rare Earth Doped Fiber Lasers)
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11 pages, 7605 KiB  
Article
1 W High Performance LED-Array Based Optical Wireless Power Transmission System for IoT Terminals
by Mingzhi Zhao and Tomoyuki Miyamoto
Photonics 2022, 9(8), 576; https://doi.org/10.3390/photonics9080576 - 16 Aug 2022
Cited by 4 | Viewed by 1553
Abstract
Optical wireless power transmission (OWPT) is a promising technology for remote energy supply, especially for powering Internet of things (IoT) terminals. Light-emitting diode (LED)-based power sources of OWPT are attractive for the development of high-performance systems without the constraints of safety issues. In [...] Read more.
Optical wireless power transmission (OWPT) is a promising technology for remote energy supply, especially for powering Internet of things (IoT) terminals. Light-emitting diode (LED)-based power sources of OWPT are attractive for the development of high-performance systems without the constraints of safety issues. In this paper, the electricity output of a near-infrared LED-OWPT is significantly improved. The saturation output caused by the small lens aperture in the LED array collimation scheme was analyzed. The experiment achieved a maximum electricity output of more than 1 W from a 50 × 50 mm2 GaAs solar cell at 1 m transmission distance. In addition, the thermal features also proved the feasibility of a high-output LED-OWPT system for practical applications. Full article
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13 pages, 7445 KiB  
Article
Shack–Hartmann Wavefront Sensing Based on Four-Quadrant Binary Phase Modulation
by Mengmeng Zhao, Wang Zhao, Kangjian Yang, Shuai Wang, Ping Yang, Fengjiao Zeng, Lingxi Kong and Chao Yang
Photonics 2022, 9(8), 575; https://doi.org/10.3390/photonics9080575 - 16 Aug 2022
Cited by 3 | Viewed by 1690
Abstract
Aiming at the problem that it is difficult for the conventional Shack–Hartmann wavefront sensor to achieve high-precision wavefront reconstruction with low spatial sampling, a kind of Shack–Hartmann wavefront sensing technology based on four-quadrant binary phase modulation is proposed in this paper. By introducing [...] Read more.
Aiming at the problem that it is difficult for the conventional Shack–Hartmann wavefront sensor to achieve high-precision wavefront reconstruction with low spatial sampling, a kind of Shack–Hartmann wavefront sensing technology based on four-quadrant binary phase modulation is proposed in this paper. By introducing four-quadrant binary phase modulation into each subaperture, the technology is able to use an optimization algorithm to reconstruct wavefronts with high precision. The feasibility and effectiveness of this method are verified at extreme low spatial frequency by a series of numerical simulations, which show that the proposed method can reliably reconstruct wavefronts with high accuracy with rather low spatial sampling. In addition, the experiment demonstrates that with a 2 × 2 microlens array, the four-quadrant binary phase-modulated Shack–Hartmann wavefront sensor is able to achieve approximately 54% reduction in wavefront reconstitution error over the conventional Shack–Hartmann wavefront sensor. Full article
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13 pages, 3846 KiB  
Article
Perfect Solar Absorber with Extremely Low Infrared Emissivity
by Zhaolong Wang, Yinbao Wei, Zhen Liu, Guihui Duan, Dongsheng Yang and Ping Cheng
Photonics 2022, 9(8), 574; https://doi.org/10.3390/photonics9080574 - 15 Aug 2022
Cited by 8 | Viewed by 1780
Abstract
We propose a multi-materials solar absorber consisting of regularly arranged cross resonators made of Ni, and nanocylinders made of Ti on their four corners. The finite difference time domain (FDTD) method is used to study the absorption performance of solar energy, the inherent [...] Read more.
We propose a multi-materials solar absorber consisting of regularly arranged cross resonators made of Ni, and nanocylinders made of Ti on their four corners. The finite difference time domain (FDTD) method is used to study the absorption performance of solar energy, the inherent absorption mechanisms and influencing factors of the absorber submerged in water. The proposed absorber achieves a nearly perfect absorption in the wavelength range of 300–2400 nm with an average absorptance higher than 98%, indicating that most of solar energy will be harvested. In addition, the high absorptance in the solar spectrum originates from the plasmon resonances of cross resonators and the magnetic polariton from the interaction between cross nanostructures and multi-material nanocylinders. Moreover, our absorbers are insensitive to the polarization of light due to the symmetry of the structures, but sensitive to the incident angle of the light. Most significantly, our absorbers can effectively prevent heat loss via radiation heat transfer by lowering their emissivity in the infrared region. The present study demonstrates a new design strategy for perfect solar absorbers consist of simple nanostructures made from multi-materials, which promise potential applications of solar energy harvesting and solar steam generation for desalination and wastewater treatment. Full article
(This article belongs to the Special Issue Artificial Photonic Structures for Energy Harvesting and Management)
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16 pages, 4976 KiB  
Article
Image Quality Assessment for Digital Volume Correlation-Based Optical Coherence Elastography
by Xianglong Lin, Jinlong Chen, Yongzheng Hu, Xiaowei Feng, Haosen Wang, Haofei Liu and Cuiru Sun
Photonics 2022, 9(8), 573; https://doi.org/10.3390/photonics9080573 - 15 Aug 2022
Cited by 2 | Viewed by 1750
Abstract
Optical coherence elastography (OCE) based on digital volume correlation (DVC) has the advantages of full 3D displacements and strain tensor quantification. However, the measurement results are often unreliable due to the poor quality of the optical coherence tomography (OCT) speckle patterns. This paper [...] Read more.
Optical coherence elastography (OCE) based on digital volume correlation (DVC) has the advantages of full 3D displacements and strain tensor quantification. However, the measurement results are often unreliable due to the poor quality of the optical coherence tomography (OCT) speckle patterns. This paper proposes an image evaluation index based on OCT-DVC (CMGG, combined mean attenuation intensity, breadth and dispersion of the gray level distribution), which comprehensively considers the OCT signals’ attenuation and the breadth and dispersion of the gray level distribution of the OCT images. Virtual deformation experiments of phantoms by numerically applied displacements and deformation measurement of pork meat were conducted. The results of the mean bias errors have a corresponding good relationship with CMGG, which demonstrates the effectiveness of the proposed CMGG. Based on this index, a lot of time may be saved by a pretest evaluation during DVC-OCE measurement. CMGG also guides the development of OCE system design, adjustment and new DVC-OCE algorithms. Full article
(This article belongs to the Special Issue Optical Elastography: Current Status and Future Applications)
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12 pages, 3390 KiB  
Article
Antisymmetric Mode Cancellation for High-Q Cavities in a Double-Disk
by Seung Hyeon Hong, Young Jin Lee, Seokhyeon Hong, Youngsoo Kim and Soon-Hong Kwon
Photonics 2022, 9(8), 572; https://doi.org/10.3390/photonics9080572 - 14 Aug 2022
Cited by 2 | Viewed by 1716
Abstract
High-quality factor dielectric microcavities like whispering-gallery-mode resonators can be widely applied in fields such as laser, optical sensor, switch, and filter. We propose the whispering-gallery-mode double-disk cavity comprising dielectric disks apart along the face of the disk. The electric field of each disk [...] Read more.
High-quality factor dielectric microcavities like whispering-gallery-mode resonators can be widely applied in fields such as laser, optical sensor, switch, and filter. We propose the whispering-gallery-mode double-disk cavity comprising dielectric disks apart along the face of the disk. The electric field of each disk with opposite phases was excited; the emitted radiation field was annihilated by destructive interference. We numerically achieved a 5.67-fold enhancement in quality factor at the double-disk cavity with a radius, thickness, and gap distance of 850 nm, 220 nm, and 220 nm, respectively, compared to a single dielectric disk with the same structural conditions. Full article
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13 pages, 4012 KiB  
Article
Demonstration of Yb-Doped Fiber Amplifier Operating near 980 nm with the Slope Efficiency Close to the Theoretical Limit
by Zhaode Li, Shangde Zhou, Aimin Liu, Jianqiu Cao, Zhihe Huang and Jinbao Chen
Photonics 2022, 9(8), 571; https://doi.org/10.3390/photonics9080571 - 12 Aug 2022
Cited by 2 | Viewed by 1736
Abstract
In this paper, the scalability of slope efficiency of a Yb-doped fiber amplifier operating near 980 nm is studied with the core-pumping scheme. By means of numerical prediction, it is found that the theoretical limit of slope efficiency should be about 92.2%. Then, [...] Read more.
In this paper, the scalability of slope efficiency of a Yb-doped fiber amplifier operating near 980 nm is studied with the core-pumping scheme. By means of numerical prediction, it is found that the theoretical limit of slope efficiency should be about 92.2%. Then, the experiment study is carried out. An 85.3% slope efficiency of emission around 980 nm is achieved with the seed light around 976.5 nm, and the strong in-band amplified spontaneous emission (ASE) is supposed to be a factor limiting the upscaling of slope efficiency. In order to suppress the in-band ASE, the double-wavelength fiber oscillator near 980 nm is fabricated and used as the seed source, with which the slope efficiency is elevated to 90.7%. Such slope efficiency is very close to the theoretical limit and sets a new record of slope efficiency for the Yb-doped fiber amplifier operating near 980 nm, to the best of our knowledge. It is also revealed that the suppression of in-band ASE should be of great importance to elevate the slope efficiency of a Yb-doped fiber amplifier operating near 980 nm. Full article
(This article belongs to the Special Issue Rare-Earth-Doped Fiber Lasers and Amplifiers)
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4 pages, 192 KiB  
Editorial
Special Issue on Polarized Light and Optical Systems
by Nikolai I. Petrov and Alexey P. Porfirev
Photonics 2022, 9(8), 570; https://doi.org/10.3390/photonics9080570 - 12 Aug 2022
Viewed by 1630
Abstract
Polarization is often measured to study the interaction of light and matter, so the description of the polarization of light beams is of both practical and fundamental interest [...] Full article
(This article belongs to the Special Issue Polarized Light and Optical Systems)
9 pages, 3512 KiB  
Communication
Yoctosecond Timing Jitter Sensitivity in Tightly Synchronized Mode-Locked Ti:Sapphire Lasers
by Hao Xu, Haitao Wu, Dong Hou, Haoyuan Lu, Zhaolong Li and Jianye Zhao
Photonics 2022, 9(8), 569; https://doi.org/10.3390/photonics9080569 - 12 Aug 2022
Cited by 2 | Viewed by 1473
Abstract
Higher sensitivity in timing jitter measurement has great importance in studies related to precise measurements. Timing jitter noise floors contribute one of the main parts in existing measurements. In this article, a phase error signal is obtained by superposition of outputs of two [...] Read more.
Higher sensitivity in timing jitter measurement has great importance in studies related to precise measurements. Timing jitter noise floors contribute one of the main parts in existing measurements. In this article, a phase error signal is obtained by superposition of outputs of two optical heterodyne discrimination apparatus to suppress the noise floor. Excess phase noise of the electrical amplifier is avoided. We demonstrate 2.6 × 10−14 fs2/Hz (~160 ys/√Hz) timing jitter noise floor between two identical 99 MHz repetition-rate mode-locked Ti:sapphire lasers after their repetition rates are tightly synchronized. The performance is extensible to reach an integrated timing jitter resolution of one attosecond. Full article
(This article belongs to the Special Issue Mode-Locked Lasers)
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19 pages, 346 KiB  
Article
Statistical Analysis of the Photon Loss in Fiber-Optic Communication
by Artur Czerwinski and Katarzyna Czerwinska
Photonics 2022, 9(8), 568; https://doi.org/10.3390/photonics9080568 - 12 Aug 2022
Cited by 4 | Viewed by 2366
Abstract
In optical communication systems, photons are lost due to the attenuation of the transmission medium. To efficiently implement quantum information protocols, we need to be able to precisely describe such processes. In this paper, we propose statistical methods to estimate the attenuation coefficient [...] Read more.
In optical communication systems, photons are lost due to the attenuation of the transmission medium. To efficiently implement quantum information protocols, we need to be able to precisely describe such processes. In this paper, we propose statistical methods to estimate the attenuation coefficient of the fiber link. By following the Beer–Lambert law, we utilize the properties of the exponential distribution to estimate the rate parameter based on observable data. In particular, we determine the explicit forms of unbiased estimators that are suitable for censored (truncated) sets of data. Moreover, we focus on minimum-variance methods that ensure a reliable estimation of the attenuation coefficient. Full article
(This article belongs to the Special Issue Photonic State Tomography: Methods and Applications)
10 pages, 247 KiB  
Article
Comparing the Accuracy of Four Intraocular Lens Formulas in Eyes with Two Types of Widely Used Monofocal Lens Implants
by Monica Malaescu, Bogdana Tabacaru, Mihnea Munteanu, Leila Al Barri, Adriana Stanila and Horia Tudor Stanca
Photonics 2022, 9(8), 567; https://doi.org/10.3390/photonics9080567 - 11 Aug 2022
Viewed by 1282
Abstract
The present study aimed to compare the accuracy of intraocular lens calculation formulas Barrett Universal II, Hoffer Q, Holladay 1, and SRK/T in the prediction of postoperative refraction for two widely used monofocal implants: SN60WF and ZCB00. All eyes were divided based on [...] Read more.
The present study aimed to compare the accuracy of intraocular lens calculation formulas Barrett Universal II, Hoffer Q, Holladay 1, and SRK/T in the prediction of postoperative refraction for two widely used monofocal implants: SN60WF and ZCB00. All eyes were divided based on axial length (<22 mm, 22–24.5 mm, and >24.5 mm) and lens type. The mean and median of the absolute refractive error (AE) were calculated for all four formulas, using manufacturer-recommended lens constants as well as optimized constants. The subgroup analysis showed that the Barrett Universal II formula had the smallest mean absolute error in three groups (with short, medium, and long axial length) before and after lens factor optimization, and Holladay 1 had the best results in two groups (of medium and long axial length), and SRK/T in one short axial length group, as well as one medium AL group after A-constant optimization. This study hints at the versatility of the Barrett Universal II formula, a fourth-generation formula that is now widely available on most optical biometers and provides a useful tool of calculation for eyes of all axial lengths even without lens constant optimization. Full article
(This article belongs to the Section Biophotonics and Biomedical Optics)
10 pages, 2426 KiB  
Article
Maritime Infrared and Visible Image Fusion Based on Refined Features Fusion and Sobel Loss
by Zongjiang Gao, Feixiang Zhu, Haili Chen and Baoshan Ma
Photonics 2022, 9(8), 566; https://doi.org/10.3390/photonics9080566 - 11 Aug 2022
Cited by 1 | Viewed by 1467
Abstract
Infrared (IR) and visible image fusion has become an important technology for maritime environment awareness. In this study, we employed refined features fusion and Sobel loss for maritime IR and visible image fusion. First, we used the encoder in Densefuse net to transform [...] Read more.
Infrared (IR) and visible image fusion has become an important technology for maritime environment awareness. In this study, we employed refined features fusion and Sobel loss for maritime IR and visible image fusion. First, we used the encoder in Densefuse net to transform the image to be fused from the pixel domain to the feature domain. Then, the features’ information was accurately measured, and the refined features were fused and sent to the decoder to reconstruct the fused images. Mixed loss, commonly employed in image fusion, eliminates the effect of different losses but also introduces hyperparameters. We innovatively used Sobel loss to measure the input and fused images to reduce the hyperparameters in the loss function. Finally, experiments were performed, and our algorithm achieved good fusion results in the qualitative and quantitative evaluations. Full article
(This article belongs to the Special Issue Optical Sensing)
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12 pages, 2667 KiB  
Article
Design of a Broadband Perfect Solar Absorber Based on a Four-Layer Structure with a Cross-Shaped Resonator and Triangular Array
by Yushan Chen, Kewei You, Jianze Lin, Junwei Zhao, Wenzhuang Ma, Dan Meng, Yuyao Cheng and Jing Liu
Photonics 2022, 9(8), 565; https://doi.org/10.3390/photonics9080565 - 11 Aug 2022
Cited by 5 | Viewed by 1722
Abstract
As solar energy is a low-cost and clean energy source, there has been a great deal of interest in how to harvest it. To absorb solar energy efficiently, we designed a broadband metamaterial absorber based on the principle of Fabry–Pérot (FP) cavities and [...] Read more.
As solar energy is a low-cost and clean energy source, there has been a great deal of interest in how to harvest it. To absorb solar energy efficiently, we designed a broadband metamaterial absorber based on the principle of Fabry–Pérot (FP) cavities and surface plasmon resonance (SPR). We propose a broadband perfect absorber consisting of a four-layer structure of silica–tungsten–silica–titanium (SiO2–W–SiO2–Ti) for the incident light wavelength range of 300–2500 nm. The structure achieves perfect absorption of incident light in the wavelength range of 351.8–2465.0 nm (absorption > 90%), with an average absorption of 96.3%. The advantage of our proposed structure is that it combines the characteristics of both high and broadband absorption, and has high overall absorption efficiency for solar radiation. It is also independent of polarization and insensitive to incident angle. We investigated how absorption was affected by different structures, materials, geometric parameters, and refractive indices for different dielectric materials, and we explored the reasons for high absorption. This structure is refractory and ultrathin, and it offers a good tradeoff between bandwidth and absorption. It therefore has premium application prospects and value. Full article
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