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In Situ Formation of SnSe2/SnSe Vertical Heterostructures toward Polarization Selectable Band Alignments

SMALL 2024年第47期20卷 e2404965页

作者： Ge, Rui Liu, Beituo Sui, Fengrui Zheng, Yufan Yu, Yilun Wang, Kaiqi Qi, Ruijuan Huang, Rong Yue, Fangyu Chu, Junhao Duan, Chun-Gang East China Normal Univ Sch Phys & Elect Sci Key Lab Polar Mat & Devices MOE Shanghai 200241 Peoples R China Chinese Acad Sci Shanghai Inst Microsyst & Informat Technol Natl Key Lab Mat Integrated Circuits Shanghai 200050 Peoples R China East China Normal Univ Chongqing Key Lab Precis Opt Chongqing Inst Chongqing 401120 Peoples R China East China Normal Univ Shanghai Ctr Brain Inspired Intelligent Mat & Devi Shanghai 200241 Peoples R China Shanghai Inst Tech Phys Natl Lab Infrared Phys Shanghai 200083 Peoples R China

2D van der Waals (vdW) layered semiconductor vertical heterostructures with controllable band alignment are highly desired for nanodevice applications including photodetection and photovoltaics. However, current 2D vdW heterostructures are mainly obtained via mechanical exfoliation and stacking process, intrinsically limiting the yield and reproducibility, hardly achieving large-area with specific orientation. Here, large-area vdW-epitaxial SnSe2/SnSe heterostructures are obtained by annealing layered SnSe. These in situ Raman analyses reveal the optimized annealing conditions for the phase transition of SnSe to SnSe2. The spherical aberration-corrected transmission electron microscopy investigations demonstrate that layered SnSe2 epitaxially forms on SnSe surface with atomically sharp interface and specific orientation. Optical characterizations and theoretical calculations reveal valley polarization of the heterostructures that originate from SnSe, suggesting a naturally adjustable band alignment between type-II and type-III, only relying on the polarization angle of incident lights. This work not only offers a unique and accessible approach to obtaining large-area SnSe2/SnSe heterostructures with new insight into the formation mechanism of vdW heterostructures, but also opens the intriguing optical applications based on valleytronic nanoheterostructures.

关键词： Cs-TEM In situ epitaxial vdW heterostructures Raman SnSe2/SnSe valley polarization semiconductor

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Tunable and stable micro-ring resonator based on thin-film lithium tantalate

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APL PHOTONICS 2024年第3期9卷

作者： Yu, Jiayang Ruan, Ziliang Xue, Yu Wang, Haohua Gan, Ranfeng Gao, Tian Guo, Changjian Chen, Kaixuan Ou, Xin Liu, Liu South China Normal Univ South China Acad Adv Optoelect Higher Educ Mega Ctr Guangdong Prov Key Lab Opt Informat Mat & Technol Sci Bldg 5 Guangzhou 510006 Peoples R China Zhejiang Univ Coll Opt Sci & Engn Int Res Ctr Adv Photon State Key Lab Extreme Photon & Instrumentat Zijingang CampusEast Bldg 5 Hangzhou 310058 Peoples R China South China Normal Univ Natl Ctr Int Res Green Optoelect Guangzhou 510006 Peoples R China Chinese Acad Sci Shanghai Inst Microsyst & Informat Technol Natl Key Lab Mat Integrated Circuits Shanghai 200050 Peoples R China Zhejiang Univ Jiaxing Res Inst Intelligent Opt & Photon Res Ctr Jiaxing Key Lab Photon Sensing & Intelligent Imagi Jiaxing 314000 Peoples R China

As ferroelectric materials, lithium tantalate and lithium niobate share similar material characteristics, such as a high Pockels effect and nonlinear optical coefficients. When compared to lithium niobate, lithium tantalate offers a higher optical damage threshold, a broader transparent window, and lower birefringence, making it a promising candidate for high-performance electro-optical photonic integrated devices. In this study, we design and successfully fabricate micro-ring resonators on an acoustic-grade lithium-tantalate-on-insulator wafer, demonstrating their tunability and dynamic modulation capabilities. Experimental results indicate that the achieved thin-film lithium tantalate based micro-ring resonator exhibits an intrinsic Q-factor of 8.4 x 10(5), corresponding to a waveguide propagation loss of 0.47 dB/cm and a tuning efficiency of 1.94 pm/V. More importantly, as compared to those based on thin-film lithium niobate, a much weaker photorefractive effect and drift phenomenon around the 1550 nm wavelength under a direct-current drive are observed in the present fabricated thin-film lithium tantalate micro-rings with a silicon oxide over-cladding and a tuning electrode on top.

关键词： Silicon wafers

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High-performance Ga2O3 solar-blind UV photodetectors via film growth regulation and surface state engineering

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MATERIALS TODAY PHYSICS 2024年 45卷

作者： Wang, Jinjin Zhang, Sai Ji, Xueqiang Li, Mengcheng Zhang, Jizhou Liu, Xue Tian, Ran Lu, Chao Tang, Weihua Li, Peigang Beijing Univ Posts & Telecommun Sch Integrated Circuits Beijing 100876 Peoples R China Beijing Univ Posts & Telecommun State Key Lab Informat Photon & Opt Commun Beijing 100876 Peoples R China Chinese Acad Sci Ctr High Entropy Energy & Syst Beijing Inst Nanoenergy & Nanosyst Beijing Key Lab Micronano Energy & Sensor Beijing 101400 Peoples R China Anhui Univ Inst Phys Sci & Informat Technol Sch Mat Sci & Engn Informat Mat & Intelligent Sensing Lab Anhui Prov Hefei 230601 Peoples R China Nanjing Univ Posts & Telecommun Coll Integrated Circuit Sci & Engn Nanjing 210023 Peoples R China

Gallium oxide (Ga2O3) 2 O 3 ) with a wide bandgap is emerging as one of the most promising candidates for solar-blind photodetectors (SBPDs). However, the practical application of Ga2O3-based 2 O 3-based SBPDs is impeded by substantial defects-related leakage currents, sluggish response speed, and high-cost, making their practical applications face great challenges. Here, we proposed strategic films growth regulation and surface state engineering to grow highquality yet economical (3-Ga2O3 2 O 3 films, thereby achieving high-performance SBPDs. High-resolution transmission electron microscopy revealed the presence of high-quality films with an extremely regular arrangement of (3-Ga2O3 2 O 3 (201) planes. The full width at half maximum and root mean square roughness values are 0.07 degrees degrees and 0.716 nm, respectively. The (3-Ga2O3 2 O 3 films demonstrated a significant reduction in VO O concentrations after O2/N2 2 /N 2 plasma treatment. This process can effectively minimize thermal damage to the sample surface while retaining highly reactive free radicals. The photocurrents of devices can be further enhanced, leading to a larger PDCRs of 8.6 x 107, 7 , through N2 2 plasma treatment. Moreover, the films effectually suppress the persistent photoconductivity effect with tau r r and tau d d values of 5.31/0.97 s and 0.49/0.87 s before and after N2 2 plasma treatment, respectively. We have demonstrated the influence mechanism of O2/N2 2 /N 2 plasma treatment on photoelectronic performance. This study provides a practical approach to growing high-quality (3-Ga2O3 2 O 3 films and preparing highperformance but low-cost Ga2O3-based 2 O 3-based SBPDs.

关键词： Solar-blind photodetectors Surface state Plasma treatment Oxygen vacancies Ga2O3

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Enhanced Magnetoimpedance Effect in Co-Based Micron Composite CoFeNiSiB Ribbon Strips Coated by Carbon and FeCoGa Nanofilms for Sensing Applications

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SENSORS 2024年第10期24卷 2961页

作者： Yang, Zhen Liu, Mengyu Chen, Jingyuan Sun, Xuecheng Lei, Chong Shen, Yuanwei Wang, Zhenbao Zhu, Mengjiao Meng, Ziqin Guangxi Normal Univ Sch Elect & Informat Engn Guangxi Key Lab Brain Inspired Comp & Intelligent Guilin 541004 Peoples R China Guangxi Normal Univ Educ Dept Guangxi Zhuang Autonomous Reg Key Lab Integrated Circuits & Microsyst Guilin 541004 Peoples R China Natl Univ Singapore Inst Hlth Innovat & Technol Singapore 117599 Singapore Shanghai Univ Microelect Res & Dev Ctr Sch Mechatron Engn & Automat Shanghai 200444 Peoples R China Shanghai Jiao Tong Univ Sch Elect Informat & Elect Engn Dept Micronano Elect Natl Key Lab Adv Micro & Nano Manufacture Technol Dongchuan Rd 800 Shanghai 200240 Peoples R China

Quenched Co-based ribbon strips are widely used in the fields of magnetic amplifier, magnetic head material, magnetic shield, electric reactor, inductance core, sensor core, anti-theft system label, and so on. In this study, Co-based composite CoFeNiSiB ribbon strips with a micron width were fabricated by micro-electro-mechanical systems (MEMS) technology. The carbon and FeCoGa nanofilms were deposited for surface modification. The effect of carbon and FeCoGa nanofilm coatings on the crystal structure, surface morphology, magnetic properties, and magnetoimpedance (MI) effect of composite ribbon strips were systematically investigated. The results show that the surface roughness and coercivity of the composite ribbon strips are minimum at a thickness of the carbon coating of 60 nm. The maximum value of MI effect is 41% at 2 MHz, which is approximately 2.4 times greater than plain ribbon and 1.6 times greater than FeCoGa-coated composite ribbon strip. The addition of a carbon layer provides a conductive path for high frequency currents, which effectively reduces the characteristic frequency of the composite ribbon strip. The FeCoGa coating is able to close the flux path and reduce the coercivity, which, in turn, increases the transverse permeability and improves the MI effect. The findings indicate that a successful combination of carbon layer and magnetostrictive FeCoGa nanofilm layer can improve the MI effect and magnetic field sensitivity of the ribbon strips, demonstrating the potential of the composite strips for local and micro area field sensing applications.

关键词： magnetoimpedance effect composite ribbon strips nanofilms sensing applications

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Novel terahertz optical switch based on PIT phenomenon and Lorentz theory

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ISCIENCE 2024年第12期27卷 111301页

作者： Zhu, Jun Chen, Xiner Qin, Liuli Guangxi Normal Univ Sch Elect & Informat Engn Guangxi Key Lab Brain Inspired Comp & Intelligent Guilin 541004 Peoples R China Guangxi Normal Univ Sch Elect & Informat Engn Sch Integrated Circuits Guilin 541004 Peoples R China Suzhou Univ Sci & Technol Sch Chem & Life Sci Key Lab Adv Electrode Mat Novel Solar Cells Petr & Suzhou 215009 Jiangsu Peoples R China Guangxi Normal Univ Sch Math & Stat Guilin 541004 Peoples R China

We propose and demonstrate a structure consisting of graphene rings and square rings that enables broadband and tunable plasmon-induced transparency (PIT) effects. Through coupled Lorentz model analysis, we attribute the transmission window at 2.1 THz to the interference between the equipartitioned exciton resonance of the graphene ring pairs and the inductive-capacitive resonance of the graphene square ring pairs. We also investigate the effect of the variation of the rotation angle of the internal graphene square ring pair on the transmission characteristics. The structure not only achieves a maximum modulation depth (MDA) of 91%, insertion loss (IL) and extinction ratio (ER) of 0.3 dB and 10.94 dB, respectively, but also achieves a maximum detection sensitivity of 0.96 THz/refractive index unit (RIU). In contrast, this study achieves more than 90% modulation amplitude in the range of 0.3 THz with a simple design structure, providing new insights for research and applications in related fields.

关键词： Physics Optics Electromagnetics

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Theoretical and simulation study of dynamically tunable sensor based on liquid crystal-modulated Fano resonator in terahertz band

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OPTICS AND LASER TECHNOLOGY 2022年 155卷

作者： Li, Xue-Shi Feng, Naixing Xu, Yuanmei Huang, Zhixiang Wen, Kunhua Xiong, Xiaoming Guangdong Univ Technol Sch Automat Guangzhou 510006 Peoples R China Anhui Univ Key Lab Intelligent Comp & Signal Proc Minist Educ Hefei 230601 Peoples R China Anhui Univ Informat Mat & Intelligent Sensing Lab Anhui Prov Hefei 230601 Peoples R China South China Normal Univ Int Acad Optoelect Zhaoqing Guangzhou 510006 Peoples R China Guangdong Univ Technol Sch Phys & Optoelect Engn Guangzhou 510006 Peoples R China Guangdong Univ Technol Sch Integrated Circuits Guangzhou 510006 Peoples R China

A liquid crystal-modulated Fano resonator is designed, which has high sensitivity, tunable operating band and adjustable sensing range at the same time. The Fano resonator is constructed by attaching a ring above a main channel and connecting a groove beneath it. With the interaction of the discrete mode provided by the ring and the continuous mode provided by the groove, a Fano resonator can be produced with a pretty high sensitivity. Moreover, by infiltrating liquid crystals into the inner layer of the ring cavity, the resonant frequency of the Fano resonator can be shifted freely by adjusting the biasing voltage across the liquid crystals. The margin of the shifted frequency can achieve 57 GHz for the first-order resonance around 1.609 THz, and 140 GHz for the second-order resonance around 2.694 THz, respectively. Meanwhile, the liquid crystal infiltrated Fano resonator achieves a favorable sensitivity in terms of figure of merit (FOM) as high as 6.02 x 104. The novel Fano resonator is pretty attractive for sensing applications that require high sensitivity, tunable operating band and adjustable sensing range at the same time, paving the way for developing flexible terahertz systems in the coming future.

关键词： Dynamically tunable sensor Liquid crystal Ultra-high sensitivity Fano resonance Terahertz

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Analogous Optical Activity in Free Space Using a Single Pancharatnam-Berry Phase Element

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LASER & PHOTONICS REVIEWS 2022年第1期16卷

作者： Liu, Sheng Qi, Shuxia Li, Peng Wei, Bingyan Chen, Peng Hu, Wei Zhang, Yi Gan, Xuetao Zhang, Peng Lu, Yanqing Chen, Zhigang Zhao, Jianlin Northwestern Polytech Univ Sch Phys Sci & Technol Key Lab Light Field Manipulat & Informat Acquisit Minist Ind & Informat Technol Xian 710129 Peoples R China Northwestern Polytech Univ Sch Phys Sci & Technol Shaanxi Key Lab Opt Informat Technol Xian 710129 Peoples R China Nanjing Univ Collaborat Innovat Ctr Adv Microstruct Key Lab Intelligent Opt Sensing & Manipulat Natl Lab Solid State Microstruct Nanjing 210093 Peoples R China Nanjing Univ Coll Engn & Appl Sci Nanjing 210093 Peoples R China Chinese Acad Sci Xian Inst Opt & Precis Mech State Key Lab Transient Opt & Photon Xian 710119 Peoples R China Nankai Univ TEDA Appl Phys Inst MOE Key Lab Weak Light Nonlinear Photon Tianjin 300457 Peoples R China Nankai Univ Sch Phys Tianjin 300457 Peoples R China San Francisco State Univ Dept Phys & Astron San Francisco CA 94132 USA

It is commonly believed that optical activity (OA) is manifested mainly in chiral media, but rare in non-chiral structures. Here, an analog of OA in free space is experimentally demonstrated by using a single liquid-crystal Pancharatnam-Berry phase element (PBPE), for which the mechanism is highly consistent with that of the traditional OA. The specifically designed PBPE supports the direction-dependent polarization rotation of a Bessel beam with controllable "rotatory power." Such a polarization rotation can be revoked by another PBPE with the same structure. Unlike in a chiral medium, this scheme shows simultaneous realization of equivalent leverotation and dextorotation merely by switching the optical element orientation, promising for applications non-magnetic optical devices such as optical isolators.

关键词： Bessel beams liquid crystal Pancharatnam-Berry phase polarization rotation

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Spatial-partition fast Fourier transform beam propagation method

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OPTIK 2021年 242卷 167234-167234页

作者： Wu, Yaoyao Chang, Jiawei Shao, Weiwei Kang, Huizhen Ma, Huihui Zhang, Tianhao Tian, Jianguo Nankai Univ Photon Res Ctr Sch Phys MOE Key Lab Weak Light Nonlinear Photon Tianjin 300071 Peoples R China Nankai Univ Tianjin Key Lab Photon Mat & Technol Informat Sci Tianjin 300071 Peoples R China Qingdao Laoshan Jinjialing Sch Qingdao 266100 Peoples R China Mil Transportat Coll Basic Dept Mil Tianjin 300161 Peoples R China Yutong Bus Co Ltd Intelligent Transportat & Autonomous Driving Dept Zhengzhou 450016 Peoples R China

In this paper, a spatial-partition fast Fourier transform beam propagation method (FFT-BPM) is proposed. The theoretical analysis of this beam propagation method is carried out, and the necessary conditions for its accurate application are derived. Through high-accuracy and highspeed simulation of the propagation of light beam in the medium with large refractive index variation, the reliability of this method is demonstrated.

关键词： FFT-BPM Spatial partition Optical propagation

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Secrecy outage analysis for cooperative NOMA systems with relay selection scheme

arXiv

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arXiv 2018年

作者： Lei, Hongjiang Yang, Zixuan Park, Ki-Hong Ansari, Imran Shafique Guo, Yongcai Pan, Gaofeng Alouini, Mohamed-Slim School of Communication and Information Engineering Chongqing Key Lab of Mobile Communications Technology Chongqing University of Posts and Telecommunications Chongqing400065 China School of Engineering University of Glasgow GlasgowG12 8QQ United Kingdom Key Laboratory of Optoelectronic Technology and Systems Education Ministry of China Chongqing University Chongqing400044 China Chongqing Key Laboratory of Nonlinear Circuits and Intelligent Information Processing Southwest University Chongqing400715 Thuwal23955-6900 Saudi Arabia

This paper considers the secrecy outage performance of a multiple-relay assisted non-orthogonal multiple access (NOMA) network over Nakagami-m fading channels. Two slots are utilized to transmit signals from the base station to destination. At the first slot, the base station broadcasts the superposition signal of the two users to all decode-and-forward relays by message mapping strategy. Then the selected relay transmits superposition signal to the two users via power-domain NOMA technology. Three relay selection (RS) schemes, i.e., optimal single relay selection (OSRS) scheme, two-step single relay selection (TSRS) scheme, and optimal dual relay selection (ODRS) scheme, are proposed and the secrecy outage performance are analyzed. As a benchmark, we also examine the secrecy outage performance of the NOMA systems with traditional multiple relays combining (TMRC) scheme in which all the relay that successfully decode signals from the source forward signals to the NOMA users with equal power. Considering the correlation between the secrecy capacity of two users and different secrecy requirement for two NOMA users, the closed-form expressions for the security outage probability (SOP) of the proposed OSRS, TSRS, and ODRS schemes along with the TMRC scheme are derived and validated via simulations. To get more insights, we also derive the closed-form expressions for the asymptotic SOP for all the schemes with fixed and dynamic power allocations. Furthermore, the secrecy diversity order (SDO) of cooperative NOMA systems is obtained. The results demonstrate that our proposed schemes can significantly enhance the secrecy performance compared to the TMRC scheme and that all the RS schemes with fixed power allocation obtain zero SDO and the OSRS scheme with dynamic power allocation obtains the same SDO as TMRC. Copyright © 2018, The Authors. All rights reserved.

关键词： Cooperative communication

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Happiness detection with facial physiological measurement from hyperspectral imaging

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COMPUTERS & ELECTRICAL ENGINEERING 2022年 103卷

作者： Hao, Min Zhang, Huiling Liu, Guangyuan Gokhale, Anu Xu, Ya Cai, Jing Xie, Desheng Southwest Univ Coll Elect & Informat Engn Chongqing 400715 Peoples R China Chongqing Key Lab Nonlinear Circuit & Intelligent Chongqing Peoples R China Chinese Acad Sci Shenzhen Inst Adv Technol Ctr High Performance Comp Shenzhen 518055 Peoples R China Illinois State Univ Dept Technol Normal IL 61790 USA Suson Co Ltd Suzhou Sichuan Peoples R China

Hyperspectral imaging technology (HSI) can be used to remotely detect emotion levels in humans based on the tissue oxygen saturation (StO2) from their faces. Our prior research demonstrated some significant differences among the variations of StO2 in different facial regions of interest (ROIs) when the subjects are truly happy. Experiment is conducted for data collection with HSI where the subjects (a total of fifty participants, who rigidly conform to the research protocol) are required to show spontaneous emotions (calm, happy, and unhappy: angry). Based on the comprehensive analysis of musculoskeletal anatomy and facial action coding system (FACS), 19 ROIs have been determined. Consequently, a 19 dimensional StO2 vector is constructed as a feature input instead of employing the entire facial region. Lastly, experimental results through basic K-Nearest Neighbor (KNN) report an average accuracy rate of 83.32% when only considering fewer StO2 features. In addition, some experiments using other advanced machine learning methods also validate its effective recognition performance with facial StO2 as an affective indicator. Our findings demonstrate the possible practical feasibility of StO2 in happiness detection.

关键词： Facial analysis Happiness detection Hyperspectral imaging Spectral Reflectance Tissue oxygen saturation

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