2024

• Record 421 of
  
  Title:Fractional Fourier-Based Frequency-Spatial-Spectral Prototype Network for Agricultural Hyperspectral Image Open-Set Classification
  
  Author Full Names:Chen, Maoyang(1,2); Feng, Shou(1,2,3); Zhao, Chunhui(1); Qu, Bo(2,4,5); Su, Nan(1); Li, Wei(3); Tao, Ran(3)

  Source Title:IEEE Transactions on Geoscience and Remote Sensing

  Language:English

  Document Type:Journal article (JA)

  Abstract:At present, hyperspectral image classification (HSIC) technology has been warmly concerned in all walks of life, especially in agriculture. However, existing classification methods operate under the closed-set assumption, which deviates from the real world with open properties. At the same time, there are more serious phenomena of different crops with similar spectrums and the same crops with different spectrum in agricultural hyperspectral data, which is also a great challenge to existing methods. In this work, a fractional Fourier-based frequency-spatial-spectral prototype network (FrFSSPN) is proposed to address the challenges of open-set HSIC in agricultural scenarios. First, fractional Fourier transform (FrFT) is introduced into the network to combine the information in the frequency domain with the spatial-spectral information, so as to expand the difference between different classes on the premise of ensuring the similarity between classes. Then, the prototype learning strategy is introduced into the network to improve the feature recognition capability of the network through prototype loss. Finally, in order to break the stubbornly closed-set property of the closed-set classification (CSC) method, the open-set recognition module is proposed. The difference between the prototype vector and the feature vector is used to judge the unknown class. Experiments on three agricultural hyperspectral datasets show that this method can effectively identify unknown classes without sacrificing the classification accuracy of closed-set, and has satisfactory classification performance. © 1980-2012 IEEE.

  Affiliations:(1) Harbin Engineering University, Coll. of Info. and Commun. Eng. and the Key Lab. of Adv. Mar. Commun. and Information Technology, Ministry of Industry and Information Technology, Harbin; 150001, China; (2) Shaanxi Key Laboratory of Optical Remote Sensing and Intelligent Information Processing, Xi'an; 710119, China; (3) Beijing Institute of Technology, School of Information and Electronics, Beijing; 100081, China; (4) Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Key Laboratory of Spectral Imaging Technology Cas, Shaanxi, Xi'an; 710119, China; (5) Xi'an Jiaotong University, Ministry of Education Key Laboratory for Intelligent Networks and Network Security, Xi'an; 710049, China

  Publication Year:2024

  Volume:62

  Start Page:1-14

  Article Number:5514014

  DOI Link:10.1109/TGRS.2024.3386566

  数据库ID（收录号）:20241615917288
• Record 422 of
  
  Title:Optimization Design of Pt/C Multilayer Supermirrors for Hard X-rays
  
  Author Full Names:Zheng, Renzhou(1); Qiang, Pengfei(1); Yan, Yongqing(1); Li, Yue(1); Zhou, Qingyong(2); Sheng, Lizhi(1)

  Source Title:Nano

  Language:English

  Document Type:Article in Press

  Abstract:Aperiodic multilayers have important applications in hard X-rays astronomical observations due to their broadband responses. This paper presents an optimization model of Pt/C power-law graded stack multilayers using the IMD software. The reflectivity expression of multilayers was derived from the reflection theory of X-ray multilayers and Fresnel recursion formulas. Then, the effects of maximum bi-layer thickness (dmax), ratio of high-density material thickness to bi-layer thickness (Γ), power-law index (c), number of bi-layers (N), grazing incidence angle (φ), interfacial roughness (σ), and photon energy (E) on the reflectivity were analyzed. The calculation results showed that the dmax, Γ and c control the shift of response range, absorption peak and Bragg peaks, respectively. And the decrease of N and increase of φ and σ can result in the reduction of reflectivity at different energies. Additionally, an optimized multilayer structure was proposed according to the extremum of merit function, which can achieve a broadband reflectivity of no less than 0.6 from 1 keV up to 80 keV. These results can provide important references for the response characteristic analysis and optimization design of multilayers. © World Scientific Publishing Company.

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics Xian Institute of Optics, Precision Mechanics Chinese Academy of Sciences, Xian; 710119, China; (2) State Key Laboratory of Geo-Information Engineering, Xian; 710000, China

  Publication Year:2024

  Article Number:2450179

  DOI Link:10.1142/S1793292024501790

  数据库ID（收录号）:20245017519343
• Record 423 of
  
  Title:All-optical neural network nonlinear activation function based on the optical bistability within a micro-ring resonator
  
  Author Full Names:Zhang, Hui(1); Wen, Jin(1,2); Wu, Zhengwei(1); Wang, Qian(1); Yu, Huimin(1); Zhang, Ying(1); Pan, Yu(1); Yin, Lan(1); Wang, Chenglong(1); Qu, Shuangchao(1)

  Source Title:Optics Communications

  Language:English

  Document Type:Journal article (JA)

  Abstract:Training all-optical neural networks in itself remains an unresolved problem, and the challenges compound when the problem is turned into the hardware implementations. In this paper, we propose a nonlinear activation function based on optical bistability within a micro-ring resonator (MRR), achieving threshold control without external modulation. Furthermore, a convolutional neural network similar to the Le-Net-5 architecture is designed, in which all nonlinear activation functions are composed of optical bistable hysteresis loop. The numerical simulation results demonstrate that the recognition rate on the Fashion-MNIST dataset can achieve 91.3%, which means that the optical neuromorphic computation can be implemented by utilizing the nonlinear optical effects themselves in the all-optical hardware. Such a scheme promises access to the all-optical neural network training in the optical hardware environment compared to numerical activation functions. © 2024 Elsevier B.V.

  Affiliations:(1) School of Science, Xi'an Shiyou University, Xi'an; 710065, China; (2) State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an; 710119, China

  Publication Year:2024

  Volume:558

  Article Number:130374

  DOI Link:10.1016/j.optcom.2024.130374

  数据库ID（收录号）:20240815608927
• Record 424 of
  
  Title:Hybrid Fiber-Single Crystal Fiber Chirped-Pulse Amplification System Emitting More Than 1.5 GW Peak Power With Beam Quality Better Than 1.3
  
  Author Full Names:Li, Feng(1); Zhao, Wei(1); Li, Qianglong(1); Zhao, Hualong(1); Wang, Yishan(1); Yang, Yang(1); Wen, Wenlong(1); Cao, Xue(1)

  Source Title:Journal of Lightwave Technology

  Language:English

  Document Type:Journal article (JA)

  Abstract:A hybrid chirped pulse amplification system composed by the monolithic fiber pre-amplifier and a two-stage single-pass single crystal fiber amplifier was demonstrated. A maximum power of 68 W at the repetition rate of 100 kHz was obtained. The laser pulses were amplified and then compressed using a 1600 line/mm grating pair compressor. A short pulse duration of 358 fs and a power of 54 W were obtained at 100 kHz, corresponding to a peak power of 1.508 GW, to the best of our knowledge, this is the highest peak power ever obtained from single crystal fiber at repetition rate above 100 kHz due to the consideration of the third order dispersion which was engraved in the stretcher and the tuning capacity of higher-order dispersion compensation of chirped fiber Bragg grating. Additionally, the beam quality better than 1.3 was obtained. This high peak power CPA system with excellent comprehensive parameters will find various applications in scientific research and industrial applications. © 1983-2012 IEEE.

  Affiliations:(1) Chinese Academy of Sciences, State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Xi'an; 710119, China

  Publication Year:2024

  Volume:42

  Issue:1

  Start Page:381-385

  DOI Link:10.1109/JLT.2023.3312399

  数据库ID（收录号）:20233814763278
• Record 425 of
  
  Title:Upconversion photoluminescence of the lanthanide-doped core–shell luminescent material for anti-counterfeiting recognition
  
  Author Full Names:Li, Dongdong(1); Zhang, Qianqian(1); Liao, Haibin(1); Fan, Qi(2); She, Jiangbo(2)

  Source Title:Optics Communications

  Language:English

  Document Type:Journal article (JA)

  Abstract:Three different NaErF4:Tm@NaREF4:Er (RE = Y, Lu, Yb) core-shell luminescent material were successfully synthesized. XRD, XPS and other characterization techniques were used to analyze the composed material, morphology, and luminous characteristics of the produced microparticles. Especially, compared with the uncoated NaErF4:Tm, the luminescence intensity of the materials with active-shell structure were increased by 2.44 times, 3.46 times, and 4.01 times respectively under 980 nm laser excitation. Moreover, the generated UCMPs were reliably employed for anti-counterfeiting recognition labels when they were used as screen-printing materials for anti-counterfeiting ink. © 2024 Elsevier B.V.

  Affiliations:(1) School of Electronic Engineering, Xi'an University of Posts and Telecommunications, Xi'an; 710121, China; (2) State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an; 710119, China

  Publication Year:2024

  Volume:573

  Article Number:130987

  DOI Link:10.1016/j.optcom.2024.130987

  数据库ID（收录号）:20243516959501
• Record 426 of
  
  Title:Enhanced Up-Conversion Emission of NaGdF4: Yb3+ /Eu3+ Crystal via Li+ Doping for Anti-Counterfeiting Application
  
  Author Full Names:Wang, Chong(1); Ren, Zhong-Xuan(1,2); Li, Dong-Dong(1); She, Jiang-Bo(2)

  Source Title:Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis

  Language:Chinese

  Document Type:Journal article (JA)

  Abstract:Rare earth luminescent materials have gradually become a research hotspot in fluorescence anti-counterfeiting because of their high purity of luminous color, long fluorescent life, stable physical-chemical properties, and low toxicity. A series of NaGdF4: Yb3 + / E u 3 + microcrystals co-doped with various Li+ concentrations were synthesized by the hydrothermal method in this paper. The samples' morphology, size, and up-conversion luminescence properties were analyzed by X-ray diffraction (X R D), scanning electron microscopy (SEM), up-conversion emission spectroscopy, and fluorescence lifetime tests. The crystal with strong luminous intensity was further applied to anti-counterfeiting identification. It shows that all the diffraction peaks of NaGdF4: Yb3 + / E u 3 + / L i + microcrystals are consistent with the standard-NaGdF4 card. No impurity peak was found in the XRD pattern. The hexagonal NaGdF4: Yb3 + / E u 3 + / L i + with high purity and crystallinity was synthesized. The SEM image of the crystal shows that the generated sample is a pure hexagonal phase, with uniform distribution, and no reunion. Co-doped Y b 3 + / E u 3 + / L i + has little effect on crystal structure, morphology and size. It can be seen from the up-conversion emission spectrum that the green luminescence intensity of 15 mol% Li+ doped NaGdF4: Y b 3 + / E u 3 + crystal is 6 times higher than that of the undoped Li+ sample. Adjust the power range of the laser to 0. 8 ~ 2 . 2 W and observe the change in UCL intensity of the samples doped with 0 mol% Li+ and 15 mol% L i + . It can be observed that with the increase of pump power, the up-conversion intensity gradually increases. The number of photons required to generate the up-conversion luminescence n is close to 2, indicating that the emission process of the sample is a two-photon process. The fluorescence lifetime of the ° Di level in the sample is about 1. 4 times that of the undoped one. Finally, the NaGdF4: 0. 2Yb/0. 02Eu/0. 15Li crystal with uniform morphology and strong luminous intensity was further applied as fluorescent ink. Screen printing technology printed The fluorescent anti-counterfeiting patterns on paper, glass and plastic. The pattern emitted bright green light under the pumping of a 980 nm laser. In the natural environment, the anti-counterfeiting pattern on the paper has good concealment. The word "safe" lenght is 5. 5 mm, and the spacing between letters is 0. 5 mm. The boundaries between letters are clear and easy to distinguish under 980 nm excitation. The plastic printed with the anti-counterfeiting pattern was exposed to the outdoor natural environment for a month, and the pattern did not change significantly. It shows that the anti-counterfeiting pattern made of NaGdF4: 0. 2Yb/0. 02Eu/0. 15Li has a high resolution, is easy to identify, and is less affected by the environment, and has excellent application prospects in anti-counterfeiting identification. © 2024 Science Press. All rights reserved.

  Affiliations:(1) School of Electronic Engineering, Xi'an University of Posts and Telecommunications, Xi'an; 710121, China; (2) State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an; 710119, China

  Publication Year:2024

  Volume:44

  Issue:2

  Start Page:497-503

  DOI Link:10.3964/j.issn.1000-0593(2024)02-0497-07

  数据库ID（收录号）:20240815615655
• Record 427 of
  
  Title:Simulation of Polarimetric Photoelectric Process in X-Ray Polarization Detector
  
  Author Full Names:Zheng, Renzhou(1); Qiang, Pengfei(1); Sheng, Lizhi(1); Yan, Yongqing(1)

  Source Title:Guangxue Xuebao/Acta Optica Sinica

  Language:Chinese

  Document Type:Journal article (JA)

  Abstract:Objective X-ray polarization detection is an important means to study the astrophysical properties of intense X-ray sources such as black holes, pulsars, and related gamma-ray bursts. The development of X-ray polarization detectors with excellent performance is the technical basis for related research. Early X-ray polarization detectors were mainly Thomson scattering polarimeters and Bragg polarimeters. However, due to the low modulation factor and narrow detection energy range, the ideal polarization measurement results were not obtained. In 2001, Costa et al. proposed a new way of X-ray polarization detection using the photoelectric effect, in which the X-ray polarization information was obtained by imaging the photoelectron track produced by X-ray photons through a gas detector. The polarimetric photoelectric process is the key physical process for the detector to realize polarization detection. It is of great significance to clarify the photon-gas interaction process and the distribution law of emitted photoelectrons for further understanding the working mechanism of the detector. The polarimetric photoelectric process is an important research content in the development of this type of X-ray polarization detector. Different types of gases have various properties, which will affect the particle transport in the polarimetric photoelectric process and further leads to different detection efficiencies. Therefore, it is necessary to simulate the polarimetric photoelectric process under different conditions. This can provide a theoretical basis and data support for the structure design of X-ray polarization detectors. Methods We simulate the polarimetric photoelectric process of 2-10 keV linearly polarized X-ray photons in several commonly used working gases by the Monte Carlo code Geant4. The selected working gas combinations include He+ C3H8, Ne+CF4, Ne+DME, Ar+CH4, Ar+CO2, Xe+CO2, CF4+C4H10, and DME+CO2. The response relationship of the emission position and azimuthal angle distribution of photoelectron with the polarization direction and energy of the incident photon is discussed. Moreover, the effects of gas thickness, gas component, gas ratio, and photon energy on the detection efficiency are analyzed. Results and Discussions First, the response relationship of the emission position and azimuthal angle distribution of the photoelectron with the polarization direction and energy of the incident photon is clarified. The emission direction distribution probability of the photoelectron is the largest in the polarization direction of the incident photon, and the azimuthal angle distribution can be approximated as a cosine squared function. With the increase in photon energy, the counts of photoelectrons at each angle decrease in different degrees, but all of them show a statistical law that the maximum values occur when the azimuthal angle is 0 or π (- π) (Fig. 6). Moreover, the effects of gas thickness, gas component, gas ratio, and photon energy on the detection efficiency are revealed and quantified. For 2 keV photons entering into 90%Ne+10%DME gas mixture, when the gas thickness is small, the detection efficiency increases rapidly with the increase in gas thickness, from less than 0. 1 at 0. 1 cm to 0. 64 at 1 cm (Fig. 7). When the gas thickness increases to 3 cm, the detection efficiency is greater than 0. 9. Then, with the increase in gas thickness, the detection efficiency gradually approaches 1. For the CF4+C4H10, Ne+CF4, Ne+DME, DME+CO2, and He+C3H8, the detection efficiency decreases with the increase in photon energy, and the large average atomic number of gas can lead to a high detection efficiency (Fig. 8). While for the Xe+CO2, Ar+CO2, and Ar+CH4, when the photon energy is greater than the binding energy of certain shell electrons of Xe or Ar atoms, the detection efficiency will be improved to a certain extent because the corresponding shell electrons begin to be ejected. In addition to the Ar+CO2 which is affected by the electron emission in K- shell, the detection efficiency in each energy range can be effectively improved by increasing the proportion of gas with high atomic number (Fig. 9). Conclusions We simulate the polarimetric photoelectric process of 2-10 keV linearly polarized X- ray photons in several commonly used working gases by the Monte Carlo code Geant4. The response relationship of the emission position and azimuthal angle distribution of the photoelectron with the polarization direction and energy of the incident photon is clarified. The emission direction distribution probability of the photoelectron is the largest on the polarization direction of the incident photon, and the azimuthal angle distribution can be approximated as a cosine squared function. With the increase in photon energy, the counts of photoelectrons at each angle decrease in different degrees, but all of them show a statistical law that the maximum values occur when the azimuthal angle is 0 or π (- π). Moreover, the effects of gas thickness, gas component, gas ratio, and photon energy on the detection efficiency are revealed and quantified. The larger gas thickness and larger average atomic number can lead to higher detection efficiency. In addition, the increase in photon energy can result in a decrease in detection efficiency. However, for the working gases composed of Xe or Ar, when the photon energy is greater than the binding energy of a certain shell electron, the detection efficiency will be improved to a certain extent because the corresponding shell electrons begin to be ejected. The results in this paper can provide some theoretical basis and data support for the structure design of X- ray polarization detectors. In the actual selection of working gases, the drift properties of electrons in gases, the effect of photoelectron drift and diffusion on track thickness and length, and the reconstruction efficiency of the track reconstruction algorithm should also be considered. © 2024 Chinese Optical Society. All rights reserved.

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Shaanxi, Xi'an; 710119, China

  Publication Year:2024

  Volume:44

  Issue:3

  Article Number:0334003

  DOI Link:10.3788/AOS231631

  数据库ID（收录号）:20241115728993
• Record 428 of
  
  Title:Research on High-Precision Quantitative Phase Microscopy Imaging Methods
  
  Author Full Names:Min, Junwei(1); Gao, Peng(2); Dan, Dan(1); Zheng, Juanjuan(2); Yu, Xianghua(1); Yao, Baoli(1)

  Source Title:Guangxue Xuebao/Acta Optica Sinica

  Language:Chinese

  Document Type:Journal article (JA)

  Abstract:Significance Phase is one of the important attributes of light waves, and its distribution directly affects the spatial resolution of optical imaging and is related to the three-dimensional topography of objects or the refractive index distribution of transparent objects. However, the phase distribution of light waves cannot be directly detected. How to accurately obtain the phase distribution of light waves has become a hotspot in the field of optics. The invention of phase-contrast microscopy has opened the curtain of phase imaging, which has epoch-making significance. It successfully converts the phase distribution of light waves into intensity changes, solving the problem of difficult direct microscopic observation of transparent samples such as cells. Nevertheless, the conversion between phase distribution and intensity change is not a linear relationship in phase contrast microscopy, resulting in phase information that cannot be observed quantitatively. By measuring the phase of light waves, the three-dimensional topography or refractive index distribution of transparent objects can be quantitatively obtained. The refractive index is one of the essential characteristic physical quantities that reflect the internal structure and state of the sample. Therefore, conducting quantitative phase microscopy methods has scientific significance. Quantitative phase imaging has important application value in industrial detection, biomedicine, special beam generation, adaptive optics imaging, and synthetic aperture telescopes. The current quantitative phase microscopy imaging technology mainly obtains the quantitative distribution of phase through interference. Therefore, factors such as the stability of interference devices, limitations on optical diffraction, phase wrapping, coherent noise generated by laser illumination, and sample refocusing during dynamic observation affect the imaging resolution and accuracy of quantitative phase microscopy. Thus, systematic and in-depth research on improving measurement accuracy and stability, spatial resolution, expanding the longitudinal measurement range, suppressing coherent noise, and autofocusing of quantitative phase microscopy imaging has been carried out. A theoretical and technical system centered on high-precision quantitative phase microscopy imaging has been formed. Progress A simultaneous phase shift digital holographic microscopy (DHM) with a common-path configuration has been proposed, which allows the object light and reference light to share the same optical path and components, solving the impact of environmental disturbances on phase imaging fundamentally (Fig. 3), simultaneously recording multiple phase-shift interferograms within one exposure and achieving real-time high-precision quantitative phase imaging. The optical path fluctuation of the system is only 3 nm within 35 min, and the real-time phase microscopy imaging accuracy reaches 4. 2 nm, which is 2. 2 times the accuracy of conventional off-axis interference quantitative phase microscopy imaging (Fig. 5). A super-resolution quantitative phase imaging method based on structural illumination has been proposed. Using the structured light illumination, the spatial resolution of quantitative phase microscopy can be doubled when the spatial frequency of the structural illumination stripe is the same as the highest spatial frequency of the microscopic objective, and super-resolution phase imaging is realized (Fig. 7). A slightly off-axis interference dual-wavelength illuminated digital holographic microscopy has been proposed to expand the longitudinal unwrapped phase measurement range from the wavelength to the micrometer level (Fig. 8), meeting the high-precision phase imaging requirements of thicker samples. Using a low-coherence LED as an illumination light source, the coherent noise in the common laser-illuminated DHM can be reduced by 68% (Fig. 10), and the signal-to-noise ratio (SNR) of images can be improved. The phase measurement accuracy is 2. 9 nm, providing a high-precision solution for the measurement of micro/nano structures and micro electro mechanical system (MEMS) surfaces. Two autofocusing methods based on dual-wavelength illumination and dual beam off-axis illumination have been proposed to meet the autofocusing requirements of high-resolution quantitative phase microscopy imaging for long-term tracking and observation of samples under different conditions (Fig. 11). The former does not rely on the characteristics of the tested sample or other prior knowledge, making it suitable for both amplitude and phase objects. The latter has a simple criterion and can easily determine the optimal imaging surface by reproducing the differences and changes between images, without the need for tedious iterative calculation and with relatively fast processing speed. Conclusions and Prospects Digital holographic microscopy is one of the representative achievements with significant influence and widespread application in the field of quantitative phase imaging, playing an increasingly important role in biomedical, material science, industrial testing, flow field display research, and other fields. We focused on the theoretical and technical issues of high-precision quantitative phase imaging and conducted systematic research on improving measurement accuracy and stability, improving lateral spatial resolution, expanding longitudinal unwrapped measurement range, suppressing coherent noise, and achieving automatic image focusing. With the promotion and application of quantitative phase microscopy imaging technology in other fields such as biological research, high-precision quantitative phase topography microscopy imaging methods will be our future research direction. It is expected that quantitative phase microscopy imaging technology can play a greater role in industrial testing, materials science, and biomedical fields, becoming an indispensable tool for studying the micro world. © 2024 Chinese Optical Society. All rights reserved.

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Shaanxi, Xi'an; 710119, China; (2) School of Physics, Xidian University, Shaanxi, Xi'an; 710071, China

  Publication Year:2024

  Volume:44

  Issue:2

  Article Number:0200003

  DOI Link:10.3788/AOS231191

  数据库ID（收录号）:20240415420637
• Record 429 of
  
  Title:Simulation Study on Pulse-Modulated RF-Driven Atmospheric Pressure Argon Dielectric Barrier Discharge
  
  Author Full Names:Qi, Bing(1,2,3); Tian, Xiao(4); Zhang, Tao(5); Wang, Yishan(1); Si, Jinhai(2); Tang, Jie(1)

  Source Title:IEEE Transactions on Plasma Science

  Language:English

  Document Type:Journal article (JA)

  Abstract:The characteristics of pulse-modulated RF-driven atmospheric pressure argon (Ar) dielectric barrier discharge (DBD) have been investigated, on the basis of a 1-D coupled fluid model. Time-domain variations of the voltage and the charge density on the dielectric surface (Vκ and σ) were obtained for different radio frequency (RF) voltage amplitudes (VRF). Furthermore, the minimum voltage amplitudes of RF maintenance discharge (VRF,min) changing with the pulse duty cycle (DR) and pulse modulated frequency (fRF,p) were discussed, and the variation of spatiotemporal average electron density with spatiotemporal average sheath voltage during the low-frequency period was studied for various DR and fRF,p. It was found that Vκ and σ cannot reach a periodic steady state for smaller VRF. When it increases to VRF,min, or even greater than VRF,min,Vκ and σ reach the steady state and the time for both to reach the steady state is advanced. When VRF is 600 V, it is shortened to 2.36 × 10-6 s (about 32 RF periods), comparing with that when VRF is 280 V. VRF,min decreases as DR increasing from 20% to 100%. The discharge is only in γ mode for smaller DR while it exists in α and γ modes for greater DR. In addition, VRF,min increases along with fRF,p growing from 0.01937 to 0.1356 MHz. When fRF,p is higher, the γ mode exists for discharge, while when it is lower, there are two modes: α and γ. © 1973-2012 IEEE.

  Affiliations:(1) Chinese Academy of Sciences, State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Xi'an; 710119, China; (2) Xi'an Jiaotong University, Faculty of Electronic and Information Engineering, Xi'an; 710049, China; (3) Xi'an University of Science and Technology, Department of Physics, Xi'an; 710059, China; (4) Xi'an Aeronautical Institute, Department of Physics, Xi'an; 710077, China; (5) Xi'an University of Science and Technology, School of Material Science and Engineering, Xi'an; 710059, China

  Publication Year:2024

  Volume:52

  Issue:7

  Start Page:2653-2660

  DOI Link:10.1109/TPS.2024.3419574

  数据库ID（收录号）:20244517316779
• Record 430 of
  
  Title:Turbulence compensation with pix-to-pix generative adversarial networks in vector vortex beams
  
  Author Full Names:Zhang, Zhi(1,2,3); Xie, Xiaoping(1,3); Si, Jinhai(2); Wang, Wei(1,3); Jia, Shuaiwei(1,3); Gao, Duorui(1,3)

  Source Title:Physica Scripta

  Language:English

  Document Type:Journal article (JA)

  Abstract:Orbital angular momentum (OAM) has significantly propelled free space optical communication (FSOC) towards achieving ultra-large transmission capacities, but mode-crosstalk in atmospheric turbulence limits its application. Here, we propose a proof-of-concept turbulence compensation approach utilizing pix-to-pix generative adversarial networks (pix2pixGAN) that does not rely on the wavefront sensor. The model captures the complex relationships between distorted optical fields and phase screens through extensive training, after which the phase screen is directly recovered from the well-trained model by identifying the corresponding distorted image to compensate for distortions. Using this model, the Strehl ratio improvement is measured at 35.7%, 8.9%, and 1.7% under three distinct turbulence conditions, respectively. Furthermore, the recognition of vector vortex beams (VVBs) integrating with the pix2pixGAN significantly improves average mode accuracy from 2% to over 99%. Additionally, the exploration of VVB-based communication further elucidates pix2pixGAN's role in enhancing communication quality. These findings suggest a potential advancement in developing a novel neural network-based strategy to compensate for transmission distortions under intense turbulence. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics, Xian Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xian; 710119, China; (2) Key Laboratory for Physical Electronics and Devices, the Ministry of Education, Shaanxi Key Laboratory of Information Photonic Technique, Xian Jiaotong University, Xian; 710049, China; (3) School of Optoelectronics, University of Chinese Academy of Sciences, Beijing; 100049, China

  Publication Year:2024

  Volume:99

  Issue:10

  Article Number:105532

  DOI Link:10.1088/1402-4896/ad74b8

  数据库ID（收录号）:20243817043606
• Record 431 of
  
  Title:Enhanced optical nonlinearity of epsilon-near-zero metasurface by quasi-bound state in the continuum
  
  Author Full Names:Shi, Wenjuan(1,2); Wang, Zhaolu(1,2); Zhang, Changchang(1,2); Zhang, Congfu(1,2); Li, Wei(1,2); Liu, Hongjun(1,3)

  Source Title:Materials Today Nano

  Language:English

  Document Type:Journal article (JA)

  Abstract:Bound states in the continuum (BICs) provide a powerful way to enhance the nonlinear properties of materials, epsilon-near-zero (ENZ) materials are considered as promising candidates with strong nonlinearities. However, the realization of BIC based on ENZ materials in the near-infrared (NIR) is very challenging due to the large loss in the NIR. Here, a high-quality quasi-BIC based on the ENZ metasurface is proposed for the first time, which is composed of patterned ENZ films embedded in a dielectric-metal hybrid structure, and realizes destructive interference between the Berreman mode and photonic mode to form the Friedrich-Wintergen BIC (FW-BIC). The electric field is strongly confined in the ENZ film, resulting in considerable field enhancement, and the nonlinear refractive index coefficient is 1.63 × 10−12 m2/W, which is three orders of magnitude larger than that of the ITO film. The instantaneous response time is 600 fs and extremely high modulation speed up to the THz level. Benefiting from the perfect absorption and narrow linewidth of quasi-BIC and the change in refractive index of the metasurface induced by Kerr nonlinearity, the absolute modulation is from near-zero to 92% with an extinction ratio of 23.2 dB. It provides a promising platform for the development of integrated ultrafast high-speed photonics. © 2024 Elsevier Ltd

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an; 710119, China; (2) University of Chinese Academy of Sciences, Beijing; 100084, China; (3) Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan; 030006, China

  Publication Year:2024

  Volume:26

  Article Number:100474

  DOI Link:10.1016/j.mtnano.2024.100474

  数据库ID（收录号）:20241315815743
• Record 432 of
  
  Title:Underwater image enhancement via color correction and multi-feature image fusion
  
  Author Full Names:Ke, Ke(1,2,4); Zhang, Biyun(3); Zhang, Chunmin(1,2); Yao, Baoli(4); Guo, Shiping(1,2); Tang, Feng(1,2)

  Source Title:Measurement Science and Technology

  Language:English

  Document Type:Journal article (JA)

  Abstract:The light attenuation underwater causes the actual underwater images to suffer from color cast, low contrast, and weak illumination. To address these issues, an effective fusion-based method is proposed, which realizes color correction (CC), brightness adjustment, contrast, and detail enhancement of underwater images. Concretely, we first design an adaptive CC method via dominant color channel judgment and lower color channel compensation. Then, we detect the brightness of each input image and propose a gamma correction function based on the gradient of the cumulative histogram to adjust the brightness of the low-light images. Subsequently, global histogram stretching and adaptive fractional differentiation techniques are employed to process the brightness-adjusted image, and then the global contrast-enhanced version and detail-enhanced version are generated respectively. To integrate the advantages of both versions, a channel fusion method based on the Lab color space is used to fuse the luminance and color of the two versions separately. The experimental results demonstrate the effectiveness of the proposed method in improving the color and illumination of underwater images, as well as enhancing the clarity of images. Moreover, the testing results on multiple datasets validate the excellent stability of this method. © 2024 IOP Publishing Ltd.

  Affiliations:(1) School of Physics, Xi'An Jiaotong University, Xi'an; 710049, China; (2) The Institute of Space Optics, Xi'An Jiaotong University, Xi'an; 710049, China; (3) BA Trading(Guangzhou) Co.,Ltd., Guangzhou; 510000, China; (4) State Key Laboratory of Transient Optics and Photonics, Xi'An Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an; 710119, China

  Publication Year:2024

  Volume:35

  Issue:9

  Article Number:096123

  DOI Link:10.1088/1361-6501/ad4dca

  数据库ID（收录号）:20242616532375