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    Dynamic shaping of vectorial optical fields based on two-dimensional blazed holographic grating
    Xinyi Wang(王心怡), Yuan Gao(高源), Zhaozhong Chen(陈召忠), Jianping Ding(丁剑平), Hui-Tian Wang(王慧田)
    Chin. Phys. B, 2020, 29 (1): 014208.   DOI: 10.1088/1674-1056/ab5a3b
    Abstract299)   HTML    PDF (2767KB)(141)      
    We propose a vectorial optical field generation system based on two-dimensional blazed grating to high-efficiently generate structured optical fields with prescribed amplitude, phase, and polarization. In this system, an optimized blazed grating hologram is written on a spatial light modulator (SLM) and can diffract the majority of the incident light into the first-order diffractions of the x and y directions, which then serve as base vectors for synthesizing desired vector beams. Compared with the conventional cosine grating used in the previous work, the proposed two-dimensional, blazed grating has a much higher efficiency. Both computer simulation and optical experiment validate that a conversion efficiency up to 5 times that of the former work is achieved. Our method can facilitate applications of the optical field manipulation.
    Atomic even-harmonic generation due to symmetry-breaking effects induced by spatially inhomogeneous field
    Yue Guo(郭月), Aihua Liu(刘爱华), Jun Wang(王俊), Xueshen Liu(刘学深)
    Chin. Phys. B, 2019, 28 (9): 094212.   DOI: 10.1088/1674-1056/ab37fa
    Abstract267)   HTML    PDF (1352KB)(161)      

    We ab initio investigate the interaction between the hydrogen atom and the inhomogeneous field which is induced by resonant plasmons within a metal nanostructure. Same as normal laser pulse (homogeneous field), only odd-harmonic generation occurs when the bow-tie nanostructure is utilized. For the single nanotip case, the even-harmonic generation can be distinctly found in the harmonic emission spectrum. By investigating the symmetry and trajectories of different inhomogeneous fields, we demonstrate that the breaking symmetry of system can enable even high harmonic generations.

    Numerical simulations of strong-field processes in momentum space
    Yan Xu(徐彦), Xue-Bin Bian(卞学滨)
    Chin. Phys. B, 2020, 29 (2): 023202.   DOI: 10.1088/1674-1056/ab6553
    Abstract286)   HTML    PDF (448KB)(159)      
    The time-dependent Schrödinger equation (TDSE) is usually treated in the real space in the textbook. However, it makes the numerical simulations of strong-field processes difficult due to the wide dispersion and fast oscillation of the electron wave packets under the interaction of intense laser fields. Here we demonstrate that the TDSE can be efficiently solved in the momentum space. The high-order harmonic generation and above-threshold ionization spectra obtained by numerical solutions of TDSE in momentum space agree well with previous studies in real space, but significantly reducing the computation cost.
    Research progress of femtosecond surface plasmon polariton
    Yulong Wang(王玉龙), Bo Zhao(赵波), Changjun Min(闵长俊), Yuquan Zhang(张聿全), Jianjun Yang(杨建军), Chunlei Guo(郭春雷), Xiaocong Yuan(袁小聪)
    Chin. Phys. B, 2020, 29 (2): 027302.   DOI: 10.1088/1674-1056/ab6717
    Abstract320)   HTML    PDF (14170KB)(232)      
    As the combination of surface plasmon polariton and femtosecond laser pulse, femtosecond surface plasmon polariton has both nanoscale spatial resolution and femtosecond temporal resolution, and thus provides promising methods for light field manipulation and light-matter interaction in extreme small spatiotemporal scales. Nowadays, the research on femtosecond surface plasmon polariton is mainly concentrated on two aspects: one is investigation and characterization of excitation, propagation, and dispersion properties of femtosecond surface plasmon polariton in different structures or materials; the other one is developing new applications based on its unique properties in the fields of nonlinear enhancement, pulse shaping, spatiotemporal super-resolved imaging, and others. Here, we introduce the research progress of properties and applications of femtosecond surface plasmon polariton, and prospect its future research trends. With the further development of femtosecond surface plasmon polariton research, it will have a profound impact on nano-optoelectronics, molecular dynamics, biomedicine and other fields.
    Creation of topological vortices using Pancharatnam-Berry phase liquid crystal holographic plates
    Xuyue Guo(郭旭岳), Jinzhan Zhong(钟进展), Peng Li(李鹏), Bingyan Wei(魏冰妍), Sheng Liu(刘圣), Jianlin Zhao(赵建林)
    Chin. Phys. B, 2020, 29 (4): 040305.   DOI: 10.1088/1674-1056/ab7805
    Abstract179)   HTML    PDF (2295KB)(131)      
    Recently, physical fields with topological configurations are evoking increasing attention due to their fascinating structures both in fundamental researches and practical applications. Therein, topological light fields, because of their unique opportunity of combining experimental and analytical studies, are attracting more interest. Here, based on the Pancharatnam-Berry (PB) phase, we report the creation of Hopf linked and Trefoil knotted optical vortices by using phase-only encoded liquid crystal (LC) holographic plates. Utilizing scanning measurement and the digital holographic interference method, we accurately locate the vortex singularities and map these topological nodal lines in three-dimensions. Compared with the common methods realized by the spatial light modulator (SLM), the phase-only LC plate is more efficient. Meanwhile, the smaller pixel size of the LC element reduces the imperfection induced by optical misalignment and pixellation. Moreover, we analyze the influence of the incident beam size on the topological configuration.
    Non-Gaussian statistics of partially coherent light inatmospheric turbulence
    Hao Ni(倪昊), Chunhao Liang(梁春豪), Fei Wang(王飞), Yahong Chen(陈亚红), Sergey A. Ponomarenko, Yangjian Cai(蔡阳健)
    Chin. Phys. B, 2020, 29 (6): 064203.   DOI: 10.1088/1674-1056/ab8373
    Abstract182)   HTML    PDF (587KB)(126)      
    We derive theoretically and verify experimentally a concise general expression for the normalized intensity correlations (IC) of partially coherent light in a weak atmospheric turbulence in the fast detector measurement regime. The derived relation reveals that the medium turbulence acts, in general, as an additional noise source enhancing the IC of partially coherent beams. The maximum of the beam IC is, in general, enhanced, causing the fields to exhibit super-Gaussian statistics. On the other hand, the relation indicates that turbulence-induced noise is negligible for sufficiently low coherence light, which reveals the condition for the turbulence-free correlation imaging.
    Hybrid vector beams with non-uniform orbital angular momentum density induced by designed azimuthal polarization gradient
    Lei Han(韩磊), Shuxia Qi(齐淑霞), Sheng Liu(刘圣), Peng Li(李鹏), Huachao Cheng(程华超), Jianlin Zhao(赵建林)
    Chin. Phys. B, 2020, 29 (9): 094203.   DOI: 10.1088/1674-1056/aba09d
    Abstract287)   HTML    PDF (11845KB)(88)      
    Based on angular amplitude modulation of orthogonal base vectors in common-path interference method, we propose an interesting type of hybrid vector beams with unprecedented azimuthal polarization gradient and demonstrate in experiment. Geometrically, the configured azimuthal polarization gradient is indicated by intriguing mapping tracks of angular polarization states on Poincaré sphere, more than just conventional circles for previously reported vector beams. Moreover, via tailoring relevant parameters, more special polarization mapping tracks can be handily achieved. More noteworthily, the designed azimuthal polarization gradients are found to be able to induce azimuthally non-uniform orbital angular momentum density, while generally uniform for circle-track cases, immersing in homogenous intensity background whatever base states are. These peculiar features may open alternative routes for new optical effects and applications.
    Visible-light all-fiber vortex lasers based on mode selective couplers
    Chuchu Dong(董楚楚), Jinhai Zou(邹金海), Hongjian Wang(王鸿健), Han Yao(尧涵), Xianglong Zeng(曾祥龙), Yikun Bu(卜轶坤), Zhengqian Luo(罗正钱)
    Chin. Phys. B, 2020, 29 (9): 094204.   DOI: 10.1088/1674-1056/aba278
    Abstract143)   HTML    PDF (1208KB)(81)      
    We demonstrate visible-light all-fiber vortex lasers by incorporating the home-made mode selective couplers (MSCs). The MSC at green or red wavebands is fabricated by specially designing and fusing a single-mode fiber (SMF) and a few-mode fiber (FMF). The MSCs inserted into visible fiber cavities act as power splitters and mode converters from the LP01 to LP11 mode at green and red wavelengths, respectively. The red-light all-fiber vortex laser is formed by a 10-cm Pr3+/Yb3+:ZBLAN fiber, a fiber Bragg grating, a fiber end-facet mirror and the MSC at 635 nm, which generates vortex beams with OAM±1 at 634.4 nm and an output power of 13 mW. The green-light all-fiber vortex laser consists of a 12-cm Ho3+:ZBLAN fiber, two fiber pigtail mirrors, and the MSC at 550 nm, which generates vortex beams with OAM±1 at 548.9 nm and an output power of 3 mW.
    Quantum plasmon enhanced nonlinear wave mixing in graphene nanoflakes
    Hanying Deng(邓寒英), Changming Huang(黄长明), Yingji He(何影记), and Fangwei Ye(叶芳伟)
    Chin. Phys. B, 2021, 30 (4): 044213.   DOI: 10.1088/1674-1056/abea8d
    Abstract89)   HTML2)    PDF (1753KB)(39)      
    A distant-neighbor quantum-mechanical method is used to study the nonlinear optical wave mixing in graphene nanoflakes (GNFs), including sum-and difference-frequency generation, as well as four-wave mixing. Our analysis shows that molecular-scale GNFs support quantum plasmons in the visible spectrum region, and significant enhancement of nonlinear optical wave mixing is achieved. Specifically, the second-and third-order wave-mixing polarizabilities of GNFs are dramatically enhanced, provided that one (or more) of the input or output frequencies coincide with a quantum plasmon resonance. Moreover, by embedding a cavity into hexagonal GNFs, we show that one can break the structural inversion symmetry and enable otherwise forbidden second-order wave mixing, which is found to be enhanced by the quantum plasmon resonance too. This study reveals that the molecular-sized graphene could be used in the quantum regime for nanoscale nonlinear optical devices and ultrasensitive molecular sensors.
    Bound states in the continuum on perfect conducting reflection gratings
    Jianfeng Huang(黄剑峰), Qianju Song(宋前举), Peng Hu(胡鹏), Hong Xiang(向红), and Dezhuan Han(韩德专)
    Chin. Phys. B, 2021, 30 (8): 084211.   DOI: 10.1088/1674-1056/abeee4
    Abstract91)   HTML0)    PDF (863KB)(62)      
    Bound states can be supported on the surface of a periodically corrugated perfect conductor known as spoof surface plasmon polaritons with their dispersion curves reside below the light line. Here we show that bound states in the continuum (BICs) can also be achieved in such systems. Two types of grating structures are proposed to suppress the radiation leakage and hence generate bound states. The first one is a simple grating with broad grooves in which multiple cavity modes are accommodated. Due to the symmetry incompatibility and the destructive interaction mainly from the TM0 and TM1 modes, BICs at the Γ point and at off-Γ points are both realized. The second one is a dimerized grating with two grooves in each unit cell. The destructive interaction between the modes in the two grooves can suppresses the radiation and BICs at the Γ point are observed. The Q factors of the whole bands can be further tuned by the dimerization strength effectively. This work may offer new opportunity for the applications of metallic grating in the low frequency bands.
    Impact of the spatial coherence on self-interference digital holography
    Xingbing Chao(潮兴兵), Yuan Gao(高源), Jianping Ding(丁剑平), and Hui-Tian Wang(王慧田)
    Chin. Phys. B, 2021, 30 (8): 084212.   DOI: 10.1088/1674-1056/abd766
    Abstract59)   HTML0)    PDF (4908KB)(39)      
    Owing to the unique feature that the signal and reference waves of self-interference digital holography (SIDH) contain the same spatial information from the same point of object, compared with conventional digital holography, the SIDH has the special spatial coherence properties. We present a statistical optics approach to analyzing the formation of cross-correlation image in SIDH. Our study reveals that the spatial coherence of illumination light can greatly influence the imaging characteristics of SIDH, and the impact extent of the spatial coherence depends substantially on the recording distance of hologram. The theoretical conclusions are supported well by numerical simulation and optical experiments.
    Polarized photoluminescence spectroscopy in WS2, WSe2 atomic layers and heterostructures by cylindrical vector beams
    Lijun Wu(吴莉君), Cuihuan Ge(葛翠环), Kai Braun, Mai He(贺迈), Siman Liu(刘思嫚), Qingjun Tong(童庆军), Xiao Wang(王笑), and Anlian Pan(潘安练)
    Chin. Phys. B, 2021, 30 (8): 087802.   DOI: 10.1088/1674-1056/abf3b6
    Abstract74)   HTML0)    PDF (1566KB)(37)      
    Due to the large exciton binding energy, two-dimensional (2D) transition metal dichalcogenides (TMDCs) provide an ideal platform for studying excitonic states and related photonics and optoelectronics. Polarization states lead to distinct light-matter interactions which are of great importance for device applications. In this work, we study polarized photoluminescence spectra from intralayer exciton and indirect exciton in WS2 and WSe2 atomic layers, and interlayer exciton in WS2/WSe2 heterostructures by radially and azimuthally polarized cylindrical vector laser beams. We demonstrated the same in-plane and out-of-plane polarization behavior from the intralayer and indirect exciton. Moreover, with these two laser modes, we obtained interlayer exciton in WS2/WSe2 heterostructures with stronger out-of-plane polarization, due to the formation of vertical electric dipole moment.
    Anisotropic photoresponse of layered rhenium disulfide synaptic transistors
    Chunhua An(安春华), Zhihao Xu(徐志昊), Jing Zhang(张璟), Enxiu Wu(武恩秀), Xinli Ma(马新莉), Yidi Pang(庞奕荻), Xiao Fu(付晓), Xiaodong Hu(胡晓东), Dong Sun(孙栋), Jinshui Miao(苗金水), and Jing Liu(刘晶)
    Chin. Phys. B, 2021, 30 (8): 088503.   DOI: 10.1088/1674-1056/abff26
    Abstract40)   HTML0)    PDF (1329KB)(14)      
    Layered ReS2 with direct bandgap and strong in-plane anisotropy shows great potential to develop high-performance angle-resolved photodetectors and optoelectronic devices. However, systematic characterizations of the angle-dependent photoresponse of ReS2 are still very limited. Here, we studied the anisotropic photoresponse of layered ReS2 phototransistors in depth. Angel-resolved Raman spectrum and field-effect mobility are tested to confirm the inconsistency between its electrical and optical anisotropies, which are along 120° and 90°, respectively. We further measured the angle-resolved photoresponse of a ReS2 transistor with 6 diagonally paired electrodes. The maximum photoresponsivity exceeds 0.515 A·W-1 along b-axis, which is around 3.8 times larger than that along the direction perpendicular to b axis, which is consistent with the optical anisotropic directions. The incident wavelength- and power-dependent photoresponse measurement along two anisotropic axes further demonstrates that b axis has stronger light-ReS2 interaction, which explains the anisotropic photoresponse. We also observed angle-dependent photoresistive switching behavior of the ReS2 transistor, which leads to the formation of angle-resolved phototransistor memory. It has simplified structure to create dynamic optoelectronic resistive random access memory controlled spatially through polarized light. This capability has great potential for real-time pattern recognition and photoconfiguration of artificial neural networks (ANN) in a wide spectral range of sensitivity provided by polarized light.
    Superchiral fields generated by nanostructures and their applications for chiral sensing
    Huizhen Zhang(张慧珍), Weixuan Zhang(张蔚暄), Saisai Hou(侯赛赛), Rongyao Wang(王荣瑶), and Xiangdong Zhang(张向东)
    Chin. Phys. B, 2021, 30 (11): 113303.   DOI: 10.1088/1674-1056/ac11df
    Abstract39)      PDF (7725KB)(14)      
    Chirality is ubiquitous in natural world. Although with similar physical and chemical properties, chiral enantiomers could play different roles in biochemical processes. Discrimination of chiral enantiomers is extremely important in biochemical, analytical chemistry, and pharmaceutical industries. Conventional chiroptical spectroscopic methods are disadvantageous at a limited detection sensitivity because of the weak signals of natural chiral molecules. Recently, superchiral fields were proposed to effectively enhance the interaction between light and molecules, allowing for ultrasensitive chiral detection. Intensive theoretical and experimental works have been devoted to generation of superchiral fields based on artificial nanostructures and their application in ultrasensitive chiral sensing. In this review, we present a survey on these works. We begin with the introduction of chiral properties of electromagnetic fields. Then, the optical chirality enhancement and ultrasensitive chiral detection based on chiral and achiral nanostructures are discussed respectively. Finally, we give a short summary and a perspective for the future ultrasensitive chiral sensing.
    Photonic-plasmonic hybrid microcavities: Physics and applications
    Hongyu Zhang(张红钰), Wen Zhao(赵闻), Yaotian Liu(刘耀天), Jiali Chen(陈佳丽), Xinyue Wang(王欣月), and Cuicui Lu(路翠翠)
    Chin. Phys. B, 2021, 30 (11): 117801.   DOI: 10.1088/1674-1056/ac0db3
    Abstract51)      PDF (4256KB)(25)      
    Photonic-plasmonic hybrid microcavities, which possess a higher figure of merit Q/V (the ratio of quality factor to mode volume) than that of pure photonic microcavities or pure plasmonic nano-antennas, play key roles in enhancing light-matter interaction. In this review, we summarize the typical photonic-plasmonic hybrid microcavities, such as photonic crystal microcavities combined with plasmonic nano-antenna, whispering gallery mode microcavities combined with plasmonic nano-antenna, and Fabry-Perot microcavities with plasmonic nano-antenna. The physics and applications of each hybrid photonic-plasmonic system are illustrated. The recent developments of topological photonic crystal microcavities and topological hybrid nano-cavities are also introduced, which demonstrates that topological microcavities can provide a robust platform for the realization of nanophotonic devices. This review can bring comprehensive physical insights of the hybrid system, and reveal that the hybrid system is a good platform for realizing strong light-matter interaction.
    Minimum structure of high-harmonic spectrafrom aligned O2 and N2 molecules
    Bo Yan(闫博), Yi-Chen Wang(王一琛), Qing-Hua Gao(高庆华), Fang-Jing Cheng(程方晶), Qiu-Shuang Jing(景秋霜), Hong-Jing Liang(梁红静), and Ri Ma(马日)
    Chin. Phys. B, 2021, 30 (11): 114213.   DOI: 10.1088/1674-1056/abfbd9
    Abstract40)      PDF (566KB)(17)      
    We experimentally investigated the high-order harmonic generation (HHG) from aligned O2 and N2 molecules in a linearly polarized laser field, and presented the dependence of the harmonic spectrum on the driving laser intensity and molecular alignment angle. The minimum position of HHG of O2 varies with changing the laser intensity, which is caused by multi-orbital interference. However, the location of the observed minimum structure in N2 harmonic spectrum remained unchanged upon changing the laser intensity. The mechanism of the spectral minimum for N2 case is regarded as a Cooper-like minimum in HHG associated with the molecular electronic structure. This work indicates that harmonic spectroscopy can effectively uncover information about molecular structure and electron dynamics.
    Theory of multiphoton photoemission disclosing excited states in conduction band of individual TiO2 nanoparticles
    Bochao Li(李博超), Hao Li(李浩), Chang Yang(杨畅), Boyu Ji(季博宇), Jingquan Lin(林景全), and Toshihisa Tomie(富江敏尚)
    Chin. Phys. B, 2021, 30 (11): 114214.   DOI: 10.1088/1674-1056/ac1b8d
    Abstract95)      PDF (695KB)(33)      
    A theory of multiphoton photoemission is derived to explain the experimentally observed monotonic decrease with the wavelength in the electron yield of TiO2 nanoparticles (NPs) by as large as four orders of magnitude. It is found that the fitting parameter corresponds to the energy position of Ti3d eg and t2g states, and the derived theory is a novel diagnostic of excited states in the conduction band, very importantly, applicable to individual NPs. The difference between four-photon slope NPs and three-photon slope NPs is attributed to the difference in defect density. The success of the theory in solving the puzzling result shows that thermal emission from high-lying levels may dominate over direct multiphoton ionization in solids when the photon number larger than four is required.
    Controlled plasmon-enhanced fluorescence by spherical microcavity
    Jingyi Zhao(赵静怡), Weidong Zhang(张威东), Te Wen(温特), Lulu Ye(叶璐璐), Hai Lin(林海), Jinglin Tang(唐靖霖), Qihuang Gong(龚旗煌), and Guowei Lyu(吕国伟)
    Chin. Phys. B, 2021, 30 (11): 114215.   DOI: 10.1088/1674-1056/ac0daa
    Abstract37)      PDF (1631KB)(12)      
    A surrounding electromagnetic environment can engineer spontaneous emissions from quantum emitters through the Purcell effect. For instance, a plasmonic antenna can efficiently confine an electromagnetic field and enhance the fluorescent process. In this study, we demonstrate that a photonic microcavity can modulate plasmon-enhanced fluorescence by engineering the local electromagnetic environment. Consequently, we constructed a plasmon-enhanced emitter (PE-emitter), which comprised a nanorod and a nanodiamond, using the nanomanipulation technique. Furthermore, we controlled a polystyrene sphere approaching the PE-emitter and investigated in situ the associated fluorescent spectrum and lifetime. The emission of PE-emitter can be enhanced resonantly at the photonic modes as compared to that within the free spectral range. The spectral shape modulated by photonic modes is independent of the separation between the PS sphere and PE-emitter. The band integral of the fluorescence decay rate can be enhanced or suppressed after the PS sphere couples to the PE-emitters, depending on the coupling strength between the plasmonic antenna and the photonic cavity. These findings can be utilized in sensing and imaging applications.