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Resonant enhancement of second harmonic generation in etchless thin film lithium niobate heteronanostructure

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Science China(Physics,Mechanics & Astronomy) 2022年第10期65卷 75-82页

作者： Zhijin Huang Kaiwen Luo Ziwei Feng Zhanyuan Zhang Yang Li Wentao Qiu Heyuan Guan Yi Xu Xiangping Li Huihui Lu guangdong provincial key laboratory of Optical Fiber Sensing and Communications Department of Optoelectronic EngineeringJinan UniversityGuangzhou 510632China guangdong provincial key laboratory of Optical Fiber Sensing and Communications Institute of Photonics TechnologyJinan UniversityGuangzhou 510632China guangdong provincial key laboratory of information photonics technology Institute of Advanced Photonics TechnologySchool of Information EngineeringGuangdong University of TechnologyGuangzhou 510006China

Lithium niobate has received interest in nonlinear frequency conversion due to its wide transparency window,from ultraviolet to mid-infrared spectral regions,and large second-order nonlinear susceptibility.However,its nanostructure is generally difficult to etch,resulting in low-Q resonance and lossy nanostructures for second harmonic generation.By applying the concept of bound states in the continuum,we performed theoretical and experimental investigations on high-Q resonant etchless thin-film lithium niobate with Si O_(2) nanostructures on top for highly efficient second harmonic generation.In the fabricated nanostructured devices,a resonance with a Q factor of 980 leads to the strong enhancement of second harmonic generation by over 1500 times compared with that in unpatterned lithium niobate thin film.Although the pump slightly deviates from central resonance,an absolute conversion efficiency of 6.87×10^(-7) can be achieved with the fundamental pump peak intensity of 44.65 MW/cm^(2),thus contributing to the normalized conversion efficiency of 1.54×10^(-5)cm^(2)/GW.Our work establishes an etchless lithium niobate device for various applications,such as integrated nonlinear nanophotonics,terahertz frequency generation,and quantum information processing.

关键词： second harmonic generation etchless thin-film lithium niobate heteronanostructure high-Q resonance

Ultra-broadband near infrared phosphor with wide spectral range and long peak wavelength achieved by double-site occupation

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Journal of Rare Earths 2023年第11期41卷 1670-1677,I0001页

作者： Shuwen Yuan Fugen Wu Jin Wang Lulu Lou Shuang Zhao Daoyun Zhu Zhongfei Mu School of Materials and Energy Guangdong University of TechnologyGuangzhou 510006China guangdong provincial key laboratory of information photonics technology Guangdong University of TechnologyGuangzhou 510006China Experimental Teaching Department Guangdong University of TechnologyGuangzhou 510006China

The miniaturization and intelligence of near infrared(NIR)devices urgently require an excellent broadband NIR phosphor.However,emission spectra of most NIR phosphors cover less than 1200 nm with a full width at half maximum(FWHM)less than 200 nm and a peak wavelength less than 900 nm.Here,we successfully developed ultra-broadband NIR phosphors ScNbO_(4):Cr^(3+)which can overcome the above shortcomings based on a double-site occupancy strategy.The phosphors achieve ultra-broadband NIR emission from 800 to 1400 nm with a peak wavelength at 980 nm.Its FWHM is up to 217 nm.The valence state of Cr ions in phosphors was analyzed.The double-site occupancy of Cr^(3+)ions in the host and the relationship between host structure and optical properties are discussed in detail.NIR light transmission experiments show that phosphors have potential application value in non-destructive analysis.This work develops an excellent NIR luminescent material and provides an efficient method to obtain ultra-broadband NIR phosphors with longer peak wavelength.

关键词： Double-site Ultra-broadband Near infrared Cr^(3+) Rare earths

High sensitivity all-fiber bend sensor based on modal interferences in a ring core fiber

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Chinese Optics Letters 2023年第5期21卷 31-36页

作者：张帆齐贝贝苏柏缙许鸥秦玉文 Institute of Advanced photonics technology School of Information Engineeringand Guangdong Provincial Key Laboratory of Information Photonics TechnologyGuangdong University of TechnologyGuangzhou 510006China

We proposed and experimentally demonstrated an all-fiber sensor for measuring bend with high sensitivity based on a ring core fiber(RCF)modal interferometer.The sensor was fabricated by splicing a segment of RCF between two pieces of multimode fiber(MMF)and single-mode fiber(SMF)at the ends of the MMF as lead-in and lead-out.Due to the first segment of the MMF,the transmitted light is coupled into the ring core,silica center,and cladding of the RCF,exciting multiple modes in the RCF.By the modal interferences in the structure,bending sensing can be realized by interrogating the intensity of the interference dip.Experimental results show a high bending sensitivity of-25.63 dB/m^(-1)in the range of 1.0954 m^(-1)to1.4696 m^(-1).In addition,the advantages of the bend sensor,such as small size,low temperature sensitivity,and simple fabrication process,can be used for curvature measurement in building health monitoring.

关键词： optical fiber sensor curvature temperature ring core fiber

Flexible rotation of transverse optical field for 2D self-accelerating beams with a designated trajectory

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Opto-Electronic Advances 2021年第3期4卷 45-52页

作者： Lei Zhu Xuesong Zhao Chen Liu Songnian Fu Yuncai Wang Yuwen Qin Wuhan National laboratory for Optoelectronics and School of Optical and Electronic InformationHuazhong University of Science and TechnologyWuhan 430074China School of information Engineering Guangdong University of Technologyand Guangdong Provincial Key Laboratory of Photonics Information TechnologyGuangzhou 510006China

Self-accelerating beams have the unusual ability to remain diffraction-free while undergo the transverse shift during the free-space propagation.We theoretically identify that the transverse optical field distribution of 2D self-accelerating beam is determined by the selection of the transverse Cartesian coordinates,when the caustic method is utilized for its trajectory design.Based on the coordinate-rotation method,we experimentally demonstrate a scheme to flexibly manipulate the rotation of transverse optical field for 2D self-accelerating beams under the condition of a designated trajectory.With this scheme,the transverse optical field can be rotated within a range of 90 degrees,especially when the trajectory of 2D self-accelerating beams needs to be maintained for free-space photonic interconnection.

关键词： self-accelerating beams optical field caustic

Human action recognition using a time-delayed photonic reservoir computing

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Science China(information Sciences) 2023年第11期66卷 309-310页

作者： Chao KAI Pu LI Yi YANG Bingjie WANG K.Alan SHORE Yuncai WANG key laboratory of Advanced Transducers and Intelligent Control System Ministry of Education Taiyuan University of Technology Guangdong Provincial Key Laboratory of Photonics Information Technology School of Information Engineering 3. School of Computer Science and Electronic Engineering Bangor University

Human action recognition(HAR) has important applications, including video retrieval, entertainment, autonomous navigation systems, and visual surveillance systems [1]. Unfortunately, accurate and efficient HAR remains a challenging task in the field of computer vision because its modeling and characteristic representation belong to threedimensional space-time instead of common two-dimensional space [2].

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Sensitivity-Enhanced Hot-Wire Anemometer by Using Cladding-Etched Fiber Bragg Grating

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Photonic Sensors 2023年第3期13卷 1-7页

作者： Yuhan TANG Xuke CHEN Jiarui ZHANG Dajuan LV Liangming XIONG Xinyong DONG School of Physics and Optoelectronic Engineering Guangdong University of TechnologyGuangzhou 510006China guangdong provincial key laboratory of information photonics technology Guangzhou 510006China Institute of Optoelectronic technology China Jiliang UniversityHangzhou 310018China School of information Engineering Guangdong University of TechnologyGuangzhou 510006China State key laboratory of Optical Fiber and Cable Manufacture technology Wuhan 430073China Southern Marine Science and Engineering guangdong laboratory Zhuhai 519000China

A sensitivity-enhanced hot-wire anemometer based on a cladding-etched optical fiber Bragg grating(FBG)coated with a layer of silver film and optically heated by using a 1480nm laser diode is demonstrated.The silver film absorbs the laser power to heat the FBG to a certain high temperature and the airflow cools down the FBG hot-wire with the cooling effect and hence the Bragg wavelength of the FBG is determined by the airflow velocity.Experimental measurement results show that the heating efficiency of the FBG hot wire is improved by 3.8times in magnitude by etching the fiber cladding from 125μm down to 73.4μm,and the achieved airflow velocity sensitivities,under a laser power of 200mW,are–3180pm/(m/s),–889pm/(m/s),–268pm/(m/s),and–8.7pm/(m/s)at different airflow velocities of 0.1m/s,0.5m/s,1.5m/s,and 17m/s,respectively.In comparison,the sensitivities are only–2193 pm/(m/s),–567 pm/(m/s),–161 pm/(m/s),and–4.9pm/(m/s)for the reference anemometer without cladding etching even at a much higher heating laser power of 530mW.These results prove that the method by using a cladding-etched FBG to improve sensitivity of FBG-based hot-wire anemometers works and the sensitivity is improved significantly.

关键词： Fiber Bragg grating hot-wire anemometer optical fiber sensors

Linear shallow neural network to accelerate transmitter dispersion eye closure quaternary(TDECQ) assessment

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Science China(information Sciences) 2024年第4期67卷 337-338页

作者： Junjiang XIANG Zejun CHEN Yijun CHENG Hailin YANG Xuancheng HUO Meng XIANG Gai ZHOU Yuwen QIN Songnian FU Institute of Advanced photonics technology School of Information EngineeringGuangdong University of Technology School of Optical and Electronic information Huazhong University of Science and Technology key laboratory of Photonic technology for Integrated Sensing and Communication Ministry of Education of ChinaGuangdong University of Technology guangdong provincial key laboratory of information photonics technology Guangdong University of Technology

To support the ever-emerging capacity requirement of datacenter interconnection(DCI) applications, transmitter dispersion eye closure quaternary(TDECQ) has been proposed by IEEE802.3 standard [1], which is specifically employed for the four-level pulse amplitude modulation(PAM-4) signals. However, the traditional scheme of TDECQ assessment needs several iterative operations,

关键词： IEEE Standards

Scalable parallel ultrafast optical random bit generation based on a single chaotic microcomb

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Light(Science & Applications) 2024年第4期13卷 637-644页

作者： Pu Li Qizhi Li Wenye Tang Weiqiang Wang Wenfu Zhang Brent ELittle Sai Tek Chu KAlan Shore Yuwen Qin Yuncai Wang Institute of Advanced photonics technology School of Information EngineeringGuangdong University of TechnologyGuangzhou 51006China. key laboratory of Photonic technology for Integrated Sensing and Communication Ministry of Education of ChinaGuangdong University of TechnologyGuangzhou 51006China. guangdong provincial key laboratory of information photonics technology Guangdong University of TechnologyGuangzhou 51006China. key laboratory of Advanced Transducers andIntelligent Control System Ministry of EducationTaiyuan University of TechnologyTaiyuan 030024China. State key laboratory of Transient Optics and photonics Xi’an Institute of Optics and Precision MechanicsChinese Academy of SciencesXi’an 710119China. Department of Physics and Materials Science City University of Hong KongHong KongChina. School of Electronic Engineering Bangor UniversityBangorWales LL571UTUK

Random bit generators are critical for information security,cryptography,stochastic modeling,and simulations.Speed and scalability are key challenges faced by current physical random bit generation.Herein,we propose a massively parallel scheme for ultrafast random bit generation towards rates of order 100 terabit per second based on a single micro-ring resonator.A modulation-instability-driven chaotic comb in a micro-ring resonator enables the simultaneous generation of hundreds of independent and unbiased random bit streams.A proof-of-concept experiment demonstrates that using our method,random bit streams beyond 2 terabit per second can be successfully generated with only 7 comb lines.This bit rate can be easily enhanced by further increasing the number of comb lines used.Our approach provides a chip-scale solution to random bit generation for secure communication and high-performance computation,and offers superhigh speed and large scalability.

关键词： resonator random chaotic

Fiber laser technologies for photoacoustic microscopy

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Visual Computing for Industry,Biomedicine,and Art 2021年第1期4卷 91-103页

作者： Long Jin Yizhi Liang guangdong provincial key laboratory of Fiber Optic Sensing and Communications Institute of Photonics TechnologyJinan UniversityGuangzhou 510632China

Fiber laser technology has experienced a rapid growth over the past decade owing to increased applications in precision measurement and optical testing,medical care,and industrial applications,including laser welding,cleaning,and manufacturing.A fiber laser can output laser pulses with high energy,a high repetition rate,a controllable wavelength,low noise,and good beam quality,making it applicable in photoacoustic imaging.Herein,recent developments in fiber-laser-based photoacoustic microscopy(PAM)are reviewed.Multispectral PAM can be used to image oxygen saturation or lipid-rich biological tissues by applying a Q-switched fiber laser,a stimulated Raman scattering-based laser source,or a fiber-based supercontinuum source for photoacoustic excitation.PAM can also incorporate a single-mode fiber laser cavity as a high-sensitivity ultrasound sensor by measuring the acoustically induced lasing-frequency shift.Because of their small size and high flexibility,compact head-mounted,wearable,or hand-held imaging modalities and better photoacoustic endoscopes can be enabled using fiber-laser-based PAM.

关键词： Fiber lasers Fiber sensors Photoacoustic imaging Photoacoustic microscopy