基于空间光场调控技术的光学微操纵

光镊技术具有无机械接触与高精度操纵微小尺度粒子的优点,自发明以来已逐渐成为生命科学和胶体物理学等领域中强有力的研究工具。随着研究的深入,传统的单光阱光镊已难以满足更高级的应用需求。近年来,空间光场调控技术通过对光场的振幅、相位和偏振态分布的调制,极大地丰富和增强了光学微操纵技术的功能,促进了包括激光微纳加工、微粒分选与输运、胶体粒子物理特性研究等方面的发展。从光场的振幅、相位和偏振态调制技术出发,综述近年来空间光场调控技术的发展及其在光学微操纵中的应用,重点介绍全息光镊、特殊模式光束微操纵、矢量光场微操纵等光学微操纵技术的研究进展。     

微纳光学结构与太赫兹辐射产生技术的研究进展

太赫兹(THz)技术在基础研究与产业应用中具有重要研究意义,但其广泛应用仍受限于高效、紧凑的THz源,特别是0.5～2.0 THz波段。目前,人们已经采用了多种技术产生THz辐射,基于光学的方法是其中最重要的手段。首先,针对THz脉冲波及连续波,基于光电导效应及非线性光学差频的THz辐射产生机理,总结了近年来微纳光学结构在提高泵浦光至THz转换效率上的应用。然后,分析了金属纳米光天线通过增强泵浦光局域电场提高THz辐射效率和将金属纳米光天线作为THz辐射源两种增强情况。最后,展望了其他类型的光学微纳结构,尤其是全介质光学天线支持的米氏谐振、无辐射模式以及连续域中束缚态等新颖物理现象在THz辐射产生中的增强作用。     

基于可调谐复振幅滤波器的超长焦深矢量光场

根据矢量光场衍射积分理论和离散复振幅光瞳滤波原理, 通过一种由双λ/2波片和离散复振幅滤波器组成的可调谐复振幅滤波器, 研究了大数值孔径下超长焦深聚焦矢量光场的构建与调控. 给出了一个六环带区的离散复振幅滤波器, 对入射光场的偏振态、振幅滤波和相位滤波三者进行同步优化, 获得了焦深接近10λ的三维平顶光场; 通过调控双λ/2波片夹角来改变聚焦光场的矢量化结构, 使之在光针场、平顶光场、光管场及中间结构光场之间交替变化. 研究结果揭示了入射光场矢量化结构演化与聚焦光场矢量化结构变换之间的关系, 解决了获取动态的、可调控的超长焦深聚焦光场的问题. 两种基本的聚焦光场光针场、光管场的独自使用或三维平顶光场的调和使用, 将会在光学显微、光学微纳操控以及光学精细加工领域获得重要应用.     

新型矢量光场调控:简介、进展与应用

作为光的一个基本属性,偏振态提供的自由度对光场调控具有重要作用。具有空间结构偏振态分布的矢量光场因其具有不同于传统标量光场的独特性质而被应用于诸多领域,但矢量光场的早期研究主要集中于柱对称的局域线偏振矢量光场。近年来,偏振态分布更加丰富的新型矢量光场逐渐得到关注,这些新型矢量光场的出现丰富了矢量光场的种类并提供了新的调控自由度,被应用于焦场调控、光学微加工、光学微操纵和光信息传输等领域。综述了近年来出现的新型矢量光场,包括柱坐标系中的杂化偏振矢量光场、庞加莱球相关的矢量光场、阵列矢量光场、多奇点矢量光场和其他非柱对称的矢量光场,介绍了其进展、设计方案、实验生成、性质和相关应用。     

“超构表面2.0”专刊序

正伴随着人工智能、5G通讯以及高端芯片等信息技术的飞速发展,大容量大带宽的光学信息传输、处理和存储技术成为必然趋势。对高性能和高集成度的光学信息技术以及轻量化、微型化和集成化的纳米光学器件的迫切需求,驱动研究人员不断开发微纳尺度下的光场调控技术。然而,自然材料远远不能满足人们对微纳尺度下光场灵活多样的调控需求。尽管超构材料(Metamaterials)展现出超越自然材料的物理特性及强大的光波调控能力,基于三维亚波长人工微结构的超构材料存在损耗高、加工难、不易集成等问题,这制约了其发展及实用。     

非线性光学超构表面：基础与应用

光学超构表面是一种由亚波长尺度的超构单元在面内排布而构成的准二维人工结构材料。研究人员可以通过选择超构单元的材料组成、几何形状对光的振幅、偏振、相位和频率等光场自由度进行灵活调控。聚焦于超构表面在非线性光场调控领域的原理与应用。首先,概述了非线性晶体到非线性超构表面的发展历程。然后,讨论了对称性和几何相位在非线性光学超构表面中的重要作用。最后,介绍了非线性光学超构表面在波前调控、量子信息处理和太赫兹波的产生与调控等领域中的应用。     

原子层厚度超表面光场调控原理及应用

超表面由亚波长尺度二维人工微结构构成,可以实现对光场振幅、相位、偏振等多参量进行调控,为光场调控提供了优良平台.二维材料作为一种新型层状结构材料,相对于三维体材料有着十分独特的光学和电学特性,其与超表面结合为纳米尺度平面光学器件的发展提供了新的可能.本文综述了基于原子层厚度的二维材料超表面发展,介绍了多种二维材料超表面...     

微纳光子结构中光子和激子相互作用

微纳光子结构中超强的光场局域给光和物质相互作用带来了新的研究机遇.通过设计光学模式,微纳结构中的光子和激子可以实现可逆或者不可逆的能量交换作用.本文综述了我们近年来在微纳结构,尤其是表面等离激元及其复合结构中光子和激子在强弱耦合区域的系列研究工作,如高效可调谐及方向性的单光子发射,利用电磁真空构造增强光子和激子的耦合等.这些工作为微纳尺度上光和物质作用提供了新的物理内容,在芯片上量子信息过程及可扩展的量子网络构建中有潜在应用.     

表面等离激元光热效应研究进展

表面等离激元微纳结构能够将光场束缚在亚波长尺度,实现突破光学衍射极限的光操控,并显著增强光与物质的相互作用.在基于表面等离激元机理的光电器件研究中,微纳结构的自身光吸收通常被认为是损耗,而通过光热效应,光吸收则可有效利用并转换成热能,其中的物理过程研究和应用是当前等离激元学领域的热点方向.本文回顾了近年来表面等离激元微纳结构光热效应的相关工作,聚焦于表面等离激元热效应的物理过程、热产生和热传导调控方式的研究进展.在此基础上,介绍了表面等离激元微纳结构在微纳加工、宽谱光热转换等方面的应用.     

对应于铯原子D1线连续可调谐正交压缩态光场的制备

铯原子D₁线的非经典光由于其波长接近于量子点的独特优势,在固态量子信息网络的发展中有着重要的应用前景.在之前的工作中,利用两镜连续简并光学参量振荡器中的参量下转换过程,制备出2.8 d B正交压缩真空态光场.然而,所产生光场的压缩度较低,对于对压缩光具有实用意义的可调谐性能也未做进一步探究.理论分析表明,光学参量振荡器后腔镜对信号光透射率的增加及内腔损耗的减小可以提高压缩度.因此,本文在该研究基础上,通过使用高光洁度腔镜及优化腔镜镀膜参数等方式对光学参量振荡器进行改良,降低了光学参量腔阈值,获得压缩度为3.3 d B的单模正交压缩真空光.当光学参量腔运转为参量反放大状态时,在系统稳定运行的情况下,制备的明亮压缩态光场能够连续调谐80 MHz,为其在量子信息网络中的应用奠定了良好的基础.     

Bound states in the continuum in metal—dielectric photonic crystal with a birefringent defect

By using the difference of the band structure for the TE and TM waves in the metal—dielectric photonic crystals beyond the light cone and the birefringence of the anisotropic crystal, a one-dimensional photonic system is constructed to realize the bound states in the continuum (BICs). In addition to the BICs arising from the polarization incompatibility, the Friedrich—Wintgen BICs are also achieved when the leaking TM wave is eliminated due to the destructive interference of its ordinary and extraordinary wave components in the anisotropic crystal. A modified scheme favorable for practical application is also proposed. This scheme for BICs may help to suppress the radiation loss in the metal—dielectric photonic crystal systems.     

Bound states in the continuum in open Aharonov-Bohm rings

Using the formalism of the effective Hamiltonian, we consider bound states in a continuum (BIC). They are nonhermitian effective Hamiltonian eigenstates that have real eigenvalues. It is shown that BICs are orthogonal to open channels of the leads, i.e., disconnected from the continuum. As a result, BICs can be superposed to a transport solution with an arbitrary coefficient and exist in a propagation band. The one-dimensional Aharonov-Bohm rings that are opened by attaching single-channel leads to them allow exact consideration of BICs. BICs occur at discrete values of the energy and magnetic flux; however, it’s realization strongly depends on the way to the BIC point. The text was submitted by the authors in English.     

Evolution of polarization singularities accompanied by avoided crossing in plasmonic system

The evolution of polarization singularities supported in a one-dimensional periodic plasmonic system is studied. The lateral inversion symmetry of the system, which breaks the in-plane inversion symmetry and up-down mirror symmetry simultaneously, yields abundant polarization states. A complete evolution process with geometry for the polarization states is traced. In the evolution, circularly polarized points (C points) can stem from 3 different processes. In addition to the previously reported processes occurring in an isolated band, a new type of C point appearing in two bands simultaneously due to the avoided band crossing, is observed. Unlike the dielectric system with a similar structure which only supports at-$\varGamma$ bound states in the continuum (BICs), accidental BICs off the $\varGamma$ point are realized in this plasmonic system. This work provides a new scheme of polarization manipulation for the plasmonic systems.     

Bound states in the continuum in two-dimensional serial structures

We investigate the occurrence of bound states in the continuum (BICs) in serial structures of quantum dots coupled to an external waveguide, when some characteristic length of the system is changed. By resorting to a multichannel scattering-matrix approach, we show that BICs do actually occur in two-dimensional serial structures, and that they are a robust effect. When a BIC is produced in a two-dot system, BICs also occur for several coupled dots. We also show that the complex dependence of the conductance upon the geometry of the multi-dot system allows for a simple picture in terms of the resonance pole motion in the multi-sheeted Riemann energy surface. Finally, we show that in correspondence to zero-width states for the open system one has a multiplet of degenerate eigenenergies for the associated closed serial system, thereby generalizing results previously obtained for single dots and two-dot structures.     

Fano‐Majorana Effect and Bound States in the Continuum on a Crossbar‐Shaped Quantum Dot Hybrid Structure

Transport properties are investigated through a crossbar‐shaped structure formed by a quantum dot (QD) coupled to two normal leads and embedded between two 1D topological superconductors (TSCs). Each TSC hosts Majorana‐bound states (MBSs) at its ends, which can interact between them with an effective coupling strength. A signature of bound states in continuum (BIC) is found in the MBSs spectral function. By allowing finite inter MBSs coupling, BICs splitting is observed and shows projection in transmission for asymmetric coupling case as quasi‐BICs. As a consequence, it is also shown that the Fano effect, arising from interference phenomena between MBSs hybridization trough QD, is observed with a half‐integer amplitude modulation. It is believed that the findings can help to better understand the properties of MBSs and their interplay with QDs.     

Applying the autosynchronization of waves to amplify laser radiation in waveguides

The possibility of applying the phenomenon of autosynchronization of waves in tunnel-coupled optical waveguides to amplify the laser radiation is considered. An optical amplification method of high-power laser radiation, which includes division, amplification in each channel, and the addition of amplified waves, is proposed. It increases the formation rate of the amplified directed radiation. In the proposed method, the optical waves propagate along optical waveguides made so that the tunnel optical coupling occurs between them, and these waveguides are nonlinear-optical. This method is applicable for the synchronization (phasing) of waves in fiber-optic light guides with many cores in conditions of amplifying these waves. For example, this method can be applied in erbium amplifiers with many cores.     

PT Symmetry Induced Rings of Lasing Threshold Modes Embedded with Discrete Bound States in the Continuum

It is well known that spatial symmetry in a photonic crystal(PhC) slab is capable of creating bound states in the continuum(BICs),which can be characterized by topological charges of polarization vortices.Here,we show that when a PT-symmetric perturbation is introduced into the PhC slab,a new type of BICs(pt-BICs) will arise from each ordinary BIC together with the creation of rings of lasing threshold modes with pt-BICs embedded in these rings.Different from ordinary BICs,the Q-factor divergenc...     

Triple Rashba dots as a spin filter: Bound states in the continuum and Fano effect

We propose an efficient spin-filter device by exploiting bound states (BICs) in the continuum and Fano effect on a triple Rashba quantum dot molecule embedded in an Aharonov-Bohm interferometer. We find that the coexistence of a BIC and a Fano antiresonance result in polarizations close to 100% in wide regions in the space of parameters.     

光格中玻色-爱因斯坦凝聚的自旋磁子和自旋波

研究了一维光格中旋量玻色—爱因斯坦凝聚体的自旋磁子和自旋波。求出了自旋磁子和自发磁化强度。用经典方法求得了均匀体系的自旋波和能级以及激光调制下的自旋波和能级。特别是在连续极限近似下,求得了马丢函数波及其能级。