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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
    Abstract213)   HTML    PDF (2767KB)(120)      
    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
    Abstract225)   HTML    PDF (1352KB)(153)      

    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
    Abstract219)   HTML    PDF (448KB)(141)      
    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
    Abstract208)   HTML    PDF (14170KB)(190)      
    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
    Abstract122)   HTML    PDF (2295KB)(127)      
    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
    Abstract128)   HTML    PDF (587KB)(119)      
    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
    Abstract164)   HTML    PDF (11845KB)(72)      
    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
    Abstract84)   HTML    PDF (1208KB)(69)      
    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
    Abstract20)      PDF (1752KB)(7)      
    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.