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Controllable transitions among phase-matching conditions in a single nonlinear crystal

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Chinese Optics Letters 2024年第2期22卷 141-147页

作者：曾梓琦尤世欣杨子祥袁晨智由成龙金锐博 Hubei key laboratory of optical information and Pattern Recognition Wuhan Institute of TechnologyWuhan 430205China Quantum Photonics laboratory Department of Physics and AstronomyLouisiana State UniversityBaton RougeLouisiana 70803USA

Entangled photon pairs are crucial resources for quantum information processing *** the process of spontaneous parametric downconversion(SPDC),we can generate these photon pairs using bulk nonlinear ***,the crystal is designed to satisfy a specific type of phase-matching ***,we report controllable transitions among different types of phase matching in a single periodically poled potassium titanyl phosphate *** carefully selecting pump conditions,we can satisfy different phase-matching *** allows us to observe first-order Type-II,fifth-order Type-I,third-order Type-0,and fifth-order Type-II *** temperature-dependent spectra of our source were also analyzed in ***,we discussed the possibility of observing more than nine SPDCs in this *** work not only deepens the understanding of the physics behind phase-matching conditions,but also offers the potential for a highly versatile entangled biphoton source for quantum information research.

关键词： spontaneous parametric downconversion nonlinear crystals phase-matching condition

A deep learning model enabled multi-event recognition for distributed optical fiber sensing

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Science China(information Sciences) 2024年第3期67卷 291-307页

作者： Yujiao LI Xiaomin CAO Wenhao NI Kuanglu YU Institute of information Science School of Computer and Information TechnologyBeijing Jiaotong University Beijing key laboratory of Advanced information Science and Network technology Beijing Jiaotong University

Fiber optic sensors that utilize backscattered light offer distributed real-time measurements and have been seen tremendous improvements in sensing distance and spatial resolution over the last ***, these improvements in sensor capabilities lead to a significant increase in the amount of data that needs to be processed. Traditional processing schemes are no longer adequate, so the development of novel signal processing methods is critical. Phase-sensitive optical time domain reflectometry(Φ-OTDR) is now applied in various applications for multi-event recognition, and it would usually be difficult, sometimes even unrealistic to label all the acquired samples due to its real-time and seamless monitoring nature. To fully take advantage of the information contained within the large number of unlabeled samples, which were formerly not utilized and hence wasted, we propose a semi-supervised model to boost the event classification performance of Φ-OTDR. The model extracts respectively the temporal features and the spatial bidirectional features together with a dual attention mechanism. Its classification accuracy has been improved up to 96.9%with only 1230 labeled samples. In addition, our model shows significant advantages when the number of labeled samples is reduced. Importantly, our method improves the accuracy of multi-event classification without any modification to the optical setup.

关键词： $\Phi$-OTDR event recognition semi-supervised learning mean teacher MT-ACNN-SA-BiLSTM

Gbps key rate passive-state-preparation continuous-variable quantum key distribution within an access-network area

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Photonics Research 2024年第7期12卷 1485-1493页

作者： FEIYU JI PENG HUANG TAO WANG XUEQIN JIANG GUIHUA ZENG State key laboratory of Advanced optical Communication Systems and Networks Center for Quantum Sensing and Information ProcessingSchool of Electronic Information and Electrical EngineeringShanghai Jiao Tong UniversityShanghai 200240China Shanghai Research Center for Quantum Sciences Shanghai 201315China Hefei National laboratory Hefei 230088China College of information Science and technology Donghua UniversityShanghai 201620China

The conventional Gaussian-modulated coherent-state quantum key distribution(QKD) protocol requires the sender to perform active modulations based on a true random number generator. Compared with it, the passive-state-preparation(PSP) continuous-variable quantum key distribution(CVQKD) equivalently performs modulations passively by exploring the intrinsic field fluctuations of a thermal source, which offers the prospect of chip integration QKD with low cost. In this paper, we propose and experimentally demonstrate a high-rate PSP-CVQKD scheme within an access-network area using high-bandwidth detectors in a continuous wave encoding and decoding way. By proposing effective methods for suppressing the noises during the PSP process and polarization multiplexing to decrease the photon leakage noises, we realize the high-intensity local oscillator transmission, thereby achieving coherent detection with high efficiency, low noise, and high bandwidth. The secure key rates over transmission distance of 5.005 km with and without consideration of the finite-size effect are 273.25 Mbps and 1.09 Gbps. The use of the PSP method boosts the asymptotic secret key rate of CVQKD to Gbps level for the first time, to our knowledge, within the range of the access network, which provides an effective and secure key distribution strategy for high-speed quantum cryptography access communication.

关键词： passive network distribution

Flexible one-dimensional photonic crystal films composed of chalcogenide glass and water-soluble polymer for curvature sensing

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Chinese Optics Letters 2024年第2期22卷 135-140页

作者：陈新宇黎张成赵若兰何钰何月梁治陶光明侯冲 School of optical and Electronic information Huazhong University of Science and TechnologyWuhan 430074China Wuhan National laboratory for Optoelectronics Huazhong University of Science and TechnologyWuhan 430074China key laboratory of Vascular Aging Ministry of EducationTongji Hospital Tongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430030China State key laboratory of Material processing and Die&Mould technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Shenzhen Huazhong University of Science and technology Research Institute Shenzhen 518063China

Curvature sensing plays an important role in structural health monitoring,damage detection,real-time shape control,modification,*** curvature sensors with large measurement ranges,high sensitivity,and linearity remains a major *** this study,a curvature sensor based on flexible one-dimensional photonic crystal(1D-PC)films was *** flexible 1D-PC films composed of dense chalcogenide glass and water-soluble polymer materials were fabricated by solution *** flexible 1D-PC film curvature sensor has a wide measurement range of 33-133 m-1and a maximum sensitivity of0.26 nm/m^(-1).The shift of the transmission peak varies approximately linearly with the curvature in the entire measurement *** kind of 1D-PC film curvature sensor provides a new idea for curvature sensing and measurement.

关键词： curvature sensor one-dimensional photonic crystals solution processing chalcogenide glass flexible film

Dynamic interactive bitwise meta-holography with ultra-high computational and display frame rates

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Opto-Electronic Advances 2024年第1期7卷 36-46页

作者： Yuncheng Liu Ke Xu Xuhao Fan Xinger Wang Xuan Yu Wei Xiong Hui Gao Wuhan National laboratory for Optoelectronics and School of optical and Electronic information Huazhong University of Science and TechnologyWuhan 430074China Optics Valley laboratory Wuhan 430074China

Interactive holography offers unmatched levels of immersion and user engagement in the field of future *** of the substantial progress has been made in dynamic meta-holography,the realization of real-time,highly smooth interactive holography remains a significant challenge due to the computational and display frame rate *** this study,we introduced a dynamic interactive bitwise meta-holography with ultra-high computational and display frame *** our knowledge,this is the first reported practical dynamic interactive metasurface holographic *** spa-tially divided the metasurface device into multiple distinct channels,each projecting a reconstructed *** switching states of these channels were mapped to bitwise operations on a set of bit values,which avoids complex holo-gram computations,enabling an ultra-high computational frame *** approach achieves a computational frame rate of 800 kHz and a display frame rate of 23 kHz on a low-power Raspberry Pi computational *** to this methodology,we demonstrated an interactive dynamic holographic Tetris game system that allows interactive gameplay,color display,and on-the-fly hologram *** technology presents an inspiration for advanced dynamic meta-holography,which is promising for a broad range of applications including advanced human-computer interaction,real-time 3D visualization,and next-generation virtual and augmented reality systems.

关键词： interactive display meta-holography bitwise operation ultra-high frame rate

Carbon nanofibers embedded with Fe-Co alloy nanoparticles via electrospinning as lightweight high-performance electromagnetic wave absorbers

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Rare Metals 2024年第6期43卷 2769-2783页

作者： Wen-Jun Cai Jian-Guo Jiang Zi-Dong Zhang Zi-Xuan Liu Lu-JieZhang Zhen-Kun Long Ke Bi key laboratory for Liquid-Solid Structural Evolution and processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China School of Materials Science and Engineering Shandong UniversityJinan 250061China Energy Institute Qilu University of Technology(Shandong Academy of Sciences)Jinan 250014China State key laboratory of information Photonics and optical Communications School of ScienceBeijing University of Posts and TelecommunicationsBeijing 100876China

As a lot of electromagnetic pollution and interference issues have emerged,to overcome electromagnetic interference,prevent electromagnetic hazards,and develop new high-performance electromagnetic wave(EMW)absorbers have become a significant task in the field of materials *** this paper,a three-dimensional(3D)carbon nanofibers network with core-shell structure,embedded with varied molar ratios of iron and cobalt(4:0,3:1,2:2,1:3,0:4),was effectively synthesized(Fe/Co@C-CNFs)via *** phase,microstructure,magnetic and EMW absorption properties were *** is discovered that Fe/Co@C-CNFs doped with iron:cobalt=1:1 have excellent EMW absorption *** the matching thickness is 1.08 mm,the minimum reflection loss(RL)value is-18.66 dB,while the maximum effective absorption bandwidth(EAB)reaches 4.2 GHz(13.9-18 GHz)at a thickness of 1.22 *** is owing to the absorbers'superior impedance matching and multiple reflections as well as the conductivity,dielectric,and magnetic losses of carbon nanofibers embedded with Fe-Co alloy *** addition,the radar cross section(RCS)of the absorbers has been calculated by CST Studio Suite,showing that the absorbing coating can effectively reduce the RCS at various angles,especially for Fe/Co@C-CNFs doped with iron:cobalt=1:*** findings not only provide new insights for the preparation of light-weight and high-performance electromagnetic wave absorbers,but also contribute to energy storage and conversion.

关键词： Electromagnetic wave(EMW)absorbers Fe/Co@C-CNFs Core-shell structure EMW absorbing mechanism Radar cross section(RCS)

Observing the collapse of super-Bloch oscillations in strong-driving photonic temporal lattices

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Advanced Photonics 2024年第4期6卷 14-24页

作者： Xinyuan Hu Shulin Wang Chengzhi Qin Chenyu Liu Lange Zhao Yinglan Li Han Ye Weiwei Liu Stefano Longhi Peixiang Lu Bing Wang Huazhong University of Science and technology School of Physics Wuhan National Laboratory for Optoelectronics Wuhan Institute of technology Hubei Key Laboratory of Optical Information and Pattern Recognition Politecnico di Milano Dipartimento di Fisica IFISC (UIB-CSIC) Instituto de Fisica Interdisciplinary Sistemas Complejos

Super-Bloch oscillations(SBOs) are amplified versions of direct current(dc)-driving Bloch oscillations realized under the detuned dc-and alternating current(ac)-driving electric fields. A unique feature of SBOs is the coherent oscillation inhibition via the ac-driving renormalization effect, which is dubbed as the collapse of SBOs. However, previous experimental studies on SBOs have only been limited to the weak ac-driving regime, and the collapse of SBOs has not been observed. Here, by harnessing a synthetic temporal lattice in fiber-loop systems, we push the ac-field into a strong-driving regime and observe the collapse of SBOs, which manifests as the oscillation-trajectory localization at specific ac-driving amplitudes and oscillation-direction flip by crossing collapse points. By adopting arbitrary-wave ac-driving fields, we also realize generalized SBOs with engineered collapse conditions. Finally, we exploit the oscillation-direction flip features to design tunable temporal beam routers and splitters. We initiate and demonstrate the collapse of SBOs, which may feature applications in coherent wave localization control for optical communications and signal processing.

关键词： Electric fields optical modulators Phase modulation Bessel functions optical coherence Polarization Pulse signals Solids Physical coherence Signal processing

Wide Stopband Substrate Integrated Waveguide Filter Using Bisection and Trisection Coupling in Multilayer

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Chinese Journal of Electronics 2024年第2期33卷 436-442页

作者： Peng CHU Jianguo FENG Peng ZHU Lei GUO Long ZHANG Leilei LIU Guoqing LUO Ke WU College of Electronic and optical Engineering Nanjing University of Posts and Telecommunications National and Local Joint Engineering laboratory of RF Integration and Micro-Assembly technology School of information and Communication Engineering Dalian University of Technology Guangdong Provincial key laboratory of Optoelectronic information processing Chips and Systems Sun Yat-sen University College of Electronics and information Engineering Shenzhen University School of Electronics and information Hangzhou Dianzi University Poly-Grames Research Center Polytechnique Montreal

This article presents a highly efficient method for substrate-integrated-waveguide（SIW） filters to achieve very wide stopbands. By employing the proposed trisection slots in addition to the bisection slots as the inter-coupling structures, all spurious modes below TE505 of a SIW filter working in the fundamental mode TE101（f0）can be eliminated without requiring additional structure or complex theoretical analysis, without affecting the design of the fundamental passbands, and without degrading the performance of the filters. For verification, two prototype filters are designed, fabricated, and measured with wide stopbands up to 4.15f0 and 4.83f0, respectively. The proposed technique could facilitate the development of high-performance wide-stopband SIW filters for microwave/wireless circuits and systems.

关键词： Microwave measurement Couplings Filters Prototypes Nonhomogeneous media Microwave theory and techniques Microwave circuits

Unleashing potentials with deep learning: decoding the complex events for distributed fiber optic sensing applications

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Science China(information Sciences) 2024年第5期67卷 337-338页

作者： Yujiao LI Liqin HU Kuanglu YU Institute of information Science School of Computer and Information Technology Beijing Jiaotong University Beijing key laboratory of Advanced information Science and Network technology Beijing Jiaotong University

After decades of research, distributed fiber optic sensors have become essential tools for precise long-distance measurements. They are applied across various sectors such as railway transportation, gas and petroleum, and smart grids. Signal processing, particularly in phase-sensitive optical time domain reflectometry(Φ-OTDR) event recognition and classification, is a primary research focus.

关键词： Deep learning