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High efficiency and broad bandwidth terahertz vortex beam generation based on ultra-thin transmission Pancharatnam–Berry metasurfaces 
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下载免费PDF全文 《中国物理 B》2021,30(5):58103-058103
The terahertz(THz) vortex beam generators are designed and theoretically investigated based on single-layer ultra-thin transmission metasurfaces. Noncontinuous phase changes of metasurfaces are obtained by utilizing Pancharatnam–Berry phase elements, which possess different rotation angles and are arranged on two concentric rings centered on the origin.The circularly polarized incident THz beam could be turned into a cross-polarization transmission wave, and the orbital angular momentum(OAM) varies in value by lh. The l values change from ±1 to ±5, and the maximal cross-polarization conversion efficiency that could be achieved is 23%, which nearly reaches the theoretical limit of a single-layer structure.The frequency range of the designed vortex generator is from 1.2 THz to 1.9 THz, and the generated THz vortex beam could keep a high fidelity in the operating bandwidth. The propagation behavior of the emerged THz vortex beam is analyzed in detail. Our work offers a novel way of designing ultra-thin and single-layer vortex beam generators, which have low process complexity, high conversion efficiency and broad bandwidth. 相似文献
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We propose a method for generating double-ring-shaped vector beams. A step phase introduced by a spatial light modulator(SLM) first makes the incident laser beam have a nodal cycle. This phase is dynamic in nature because it depends on the optical length. Then a Pancharatnam–Berry phase(PBP) optical element is used to manipulate the local polarization of the optical field by modulating the geometric phase. The experimental results show that this scheme can effectively create double-ring-shaped vector beams. It provides much greater flexibility to manipulate the phase and polarization by simultaneously modulating the dynamic and the geometric phases. 相似文献
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提出一种利用相位连续可调诱导产生的双艾里光束形成方形光瓶的方法。该方法首先利用二值化后的相位调制出双艾里光束,为了能够实现光瓶能量分布,一个可调控的线性因子被引入到相位调制函数中形成新改进的相位,该相位能够灵活地调节光瓶的大小。数值模拟结果表明高斯光束通过该改进相位调制,能够形成光瓶能量分布的光束。该方形光瓶光束可应用于光镊、原子捕获与操纵。 相似文献
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提出一种利用相位连续可调诱导产生的双艾里光束形成方形光瓶的方法。该方法首先利用二值化后的相位调制出双艾里光束,为了能够实现光瓶能量分布,一个可调控的线性因子被引入到相位调制函数中形成新改进的相位,该相位能够灵活地调节光瓶的大小。数值模拟结果表明高斯光束通过该改进相位调制,能够形成光瓶能量分布的光束。该方形光瓶光束可应用于光镊、原子捕获与操纵。 相似文献
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光镊利用强会聚激光对微粒产生的梯度力来捕获微粒,可以进行无损、远程操控,同时具有皮牛精度的测力特性,已经成为物理学、生命科学和胶体化学等研究领域中不可缺少的研究工具。光镊效应可以表现微小的光子动量和角动量,是物理学的重要教学工具。本文根据高斯光束传播和变换规律,设计具有稳定捕获性能的最小化光镊,并给出了典型参数。光镊系统由捕获激光、光束耦合系统、倒置生物显微镜和大数值孔径物镜组成,成像系统由物镜、摄影目镜和CCD相机组成。本光镊系统具有紧凑特性,同时通过保持物镜后瞳充满度来实现稳定捕获。在该最小光镊系统上,可以根据用户需求增加光镊阱位操控系统、刚度调节系统和其他辅助设备以满足不同操控要求,可以很好地满足科研和教学需求。 相似文献
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Mike Woerdemann Christina Alpmann Michael Esseling Cornelia Denz 《Laser u0026amp; Photonics Reviews》2013,7(6):839-854
Optical tweezers, a simple and robust implementation of optical micromanipulation technologies, have become a standard tool in biological, medical and physics research laboratories. Recently, with the utilization of holographic beam shaping techniques, more sophisticated trapping configurations have been realized to overcome current challenges in applications. Holographically generated higher‐order light modes, for example, can induce highly structured and ordered three‐dimensional optical potential landscapes with promising applications in optically guided assembly, transfer of orbital angular momentum, or acceleration of particles along defined trajectories. The non‐diffracting property of particular light modes enables the optical manipulation in multiple planes or the creation of axially extended particle structures. Alongside with these concepts which rely on direct interaction of the light field with particles, two promising adjacent approaches tackle fundamental limitations by utilizing non‐optical forces which are, however, induced by optical light fields. Optoelectronic tweezers take advantage of dielectrophoretic forces for adaptive and flexible, massively parallel trapping. Photophoretic trapping makes use of thermal forces and by this means is perfectly suited for trapping absorbing particles. Hence the possibility to tailor light fields holographically, combined with the complementary dielectrophoretic and photophoretic trapping provides a holistic approach to the majority of optical micromanipulation scenarios. 相似文献
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实现自由调控电磁波不仅具有重要的科学研究意义,而且是通讯、能源、国防等领域的迫切需求。为了解决自然材料调控电磁波能力受限的问题,人们提出了人工超构材料这一新概念,实现了负折射、光学隐身等奇异的电磁效应。然而,经过多年的发展,超构材料仍存在结构复杂、损耗偏高、难以集成调谐等挑战。最近,本团队与国际同行一起提出了超构表面的新概念。超构表面基于电磁波在平面微结构上散射时获得的界面相位突变,充分利用人工微结构的"排列序构"这一自由度,实现了对电磁波振幅、相位、偏振及波前分布的有效调控,克服了超构材料遇到的瓶颈问题。本文主要回顾了本团队在偏振调控、波前调控及动态调控等方面开展的创新性研究。 相似文献
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空心光束的产生及其在现代光学中的应用 总被引：25，自引：0，他引：25
近年来,随着激光应用技术的发展,各种中心强度为零的激光束被相继产生,并正在形成一个新颖的所谓空心光束(也称暗中空光束)的大家族。作为激光导管、光学镊子(光钳)和光学扳手,空心光束在微观粒子(如微米粒子、纳米粒子、自由电子、生物细胞和原子或分子等)的精确、无接触操纵和控制中有着广泛的应用。本文将首先给出空心光束的定义及其参数,并详细介绍各种空心光束产生的基本原理、方法及其实验结果。其次,就空心光束的分类及其应用场合进行了简单归纳与讨论。最后就空心光束在微观粒子(包括微米粒子、纳米粒子、生物细胞和自由电子等)的光学囚禁与操控中的应用进行简要综述,并就空心光束的产生与应用及其未来研究与应用前景进行了简短总结与展望。 相似文献
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Chulsoo Choi Seung‐Yeol Lee Sang‐Eun Mun Gun‐Yeal Lee Jangwoon Sung Hansik Yun Jong‐Heon Yang Hee‐Ok Kim Chi‐Young Hwang Byoungho Lee 《Advanced Optical Materials》2019,7(12)
Broadband‐operating active devices within a small‐footprint are highly on demand in various nanophotonic fields such as fiber‐optic communication systems and chip‐based integrated optical circuits. As pioneering approaches, diverse platforms of active metasurfaces (AMs) have been proposed due to their superior tunable functionality and ultra‐compact size. However, most of previous researches provide only limited operating bandwidth because they generally rely on resonant light–matter interaction between active material and plasmonic antenna. In this study, an active wavefront switching metasurface that can operate over 500 nm bandwidth at near‐infrared spectral bands is experimentally realized by utilizing nonresonant U‐shaped Ge2Sb2Te5 nanoantennas. Two different sizes of the U‐shaped antenna are designed to exhibit large transmittance contrast and their optical phases are determined by imposing the orientation angle variation. As an example of the functionality, anomalous refraction angle switching and dispersionless active hologram are demonstrated. The devices provide high signal‐to‐noise ratio (>7 dB) for overall operation bandwidth. It is believed that the proposed AMs can be an innovative platform for real device application thanks to their not only broadband and low‐noise operation but also fast speed, low power consumption switching within a small‐footprint. 相似文献
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Focal shift of hyperbolic-cosine-Gaussian beams induced by pure phase apodizer was investigated theoretically. The pure phase apodizer consists of three concentric zones: center circle zone, inner annular zone and outer annular zone. And the phase variance of the inner annular zone is adjustable. Results show that intensity peak moves far from optical aperture and then shrinks sharply for certain radii of zones with increasing phase variance of the inner annular zone. Simultaneously, one new intensity peak occurs near optical aperture, moves far from the optical aperture, and then becomes intensity maximum peak, and repeats the evolution process of the former intensity peak. Tunable focal shift occurs with focal switch. Decreasing the phase variance can change the move direction of the intensity peaks. In addition, the maximum distance between the two intensity peaks can be altered by beam parameters of cosh parts, and the distance value increases and then decreases with increasing beam parameters of cosh parts for certain radii of zones. Tunable focal shift is also discussed to construct optical tweezers. 相似文献
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近年来,随着激光应用技术的发展,各种中心强度为零的激光束被相继产生,并正在形成一个新颖的所谓空心光束(也称暗中空光束)的大家族。作为激光导管、光学镊子(光钳)和光学扳手,空心光束在微观粒子(如微米粒子、纳米粒子、自由电子、生物细胞和原子或分子等)的精确、无接触操纵和控制中有着广泛的应用。本文将首先给出空心光束的定义及其参数,并详细介绍各种空心光束产生的基本原理、方法及其实验结果。其次,就空心光束的分类及其应用场合进行了简单归纳与讨论。最后就空心光束在微观粒子(包括微米粒子、纳米粒子、生物细胞和自由电子等)的光学囚禁与操控中的应用进行简要综述,并就空心光束的产生与应用及其未来研究与应用前景进行了简短总结与展望。 相似文献
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Weiping Wan Wenhong Yang Hang Feng Yilin Liu Qihuang Gong Shumin Xiao Yan Li 《Advanced Optical Materials》2021,9(20):2100626
Metasurfaces achieving arbitrary phase profiles within ultrathin thickness, emerge as miniaturized, ultracompact, and kaleidoscopic nanophotonic platforms. However, it is often required to segment or interleave independent subarray metasurfaces to multiplex holograms in a single nanodevice, which in turn affects the device's compactness and channel capacity. Here, a flexible strategy is proposed for multiplexing vectorial holographic images by controlling the phase distributions of holographic images in far field. Benefitting from precisely controlling the phase difference of reconstructed images through the modified Gerchberg–Saxton algorithm, two different holographic images are independently designed for the circular light by two interleaved metasurfaces and an extra vectorial hologram is flexibly encrypted in far field without additional set of structures on the metasurface plane. An unlimited number of polarization can be achieved in the holographic image and additional information can be decrypted when different polarization-dependent holographic images overlap. By continually varying phase difference between the incident right and left circular polarized light, the image within the overlap area can be modulated. The silicon dielectric metahologram with record absolute multiplexed efficiency (>25%) is achieved in the experiment. This technique, as far as it is known, promises an enormous data capacity as well as a high level of information security. 相似文献
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Weiping Wan Wenhong Yang Hang Feng Yilin Liu Qihuang Gong Shumin Xiao Yan Li 《Advanced Optical Materials》2021,9(20):2170080
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A dual optical tweezers system,which consists of a doughnut mode optical tweezer (DMOT) with the azimuthally polarised trapping beam and a solid mode optical tweezer (SMOT) with the Gauss trapping beam was constructed to compare the axial trapping effect of DMOT and SMOT.The long-distance axial trapping of ST68 microbubbles (MBs) achieved by DMOT was more stable than that of SMOT.Moreover the axial trapping force measured using the viscous drag method,was depended on the diameter of the particle,the laser power,and the numerical aperture (NA) of the objective lens.The measurement of the axial trapping force and the acquisition of CCD images of trapping effect confirmed that the DMOT showed excellent axial trapping ability than SMOT.A simple and effective method is developed to improve axial trapping effect using the azimuthally polarized beam as trapping beam.This is helpful for the long-distance manipulating of particles especially polarised biological objects in axial direction. 相似文献
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Haixiang Ma Xinzhong Li Yuping Tai Hehe Li Jingge Wang Miaomiao Tang Jie Tang Yishan Wang Zhaogang Nie 《Annalen der Physik》2017,529(12)
We report on a novel optical vortex array named circular optical vortex array, which is generated by the superposition of two concentric perfect optical vortices. The circular optical vortex array has a constant topological charge of +1 or ?1, the number and sign of which are determined by the topological charges of the two perfect optical vortices. Moreover, the radius of the circular optical vortex array is easily adjusted by using the cone angle of an axicon. Furthermore, the circular optical vortex array and multiple circular optical vortex array can be rotated by changing the initial phase difference of the perfect optical vortices on demand. This work demonstrates a complex structured optical field, which is of significance for applications such as optical tweezers, micro‐particle manipulation, and optical imaging. 相似文献
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From unravelling the most fundamental phenomena to enabling applications that impact our everyday lives, the nanoscale world holds great promise for science, technology, and medicine. However, the extent of its practical realization relies on manufacturing at the nanoscale. Among the various nanomanufacturing approaches being investigated, the bottom‐up approach involving assembly of colloidal nanoparticles as building blocks is promising. Compared to a top‐down lithographic approach, particle assembly exhibits advantages such as smaller feature size, finer control of chemical composition, less defects, lower material wastage, and higher scalability. The capability to assemble colloidal particles one by one or “digitally” has been heavily sought as it mimics the natural method of making matter and enables construction of nanomaterials with sophisticated architectures. An insight into the tools and techniques for digital assembly of particles, including their working mechanisms and demonstrated particle assemblies, is provided. Examples of nanomaterials and nanodevices are presented to demonstrate the strength of digital assembly in nanomanufacturing. 相似文献