Floquet规范转变诱导拓扑π模产生的理论分析

拓扑绝缘体是一类内部绝缘而在表面可以导电的物态,其倒空间的能带具有非平庸的拓扑特性,而在其实空间的边界上具有可以单向传播的边界态。这种拓扑界面态出现往往依赖于界面处的拓扑相变。而最近有研究在一类Floquet的拓扑体系中实验观测到一种规范场相变诱导产生的拓扑π模,这种拓扑态的产生可能不依赖于拓扑相变。本文对于这种规范场诱导的拓扑π模的产生机理做出了理论解释。两个Floquet规范相反的体系的哈密顿量由于规范相变而具有相反的π能隙质量项,类似于Jackiw-Rebbi模型,从而导致拓扑界面态的出现。本文的研究为规范场相变诱导拓扑模式的产生提供了理论基础,并加深了人们对于Floquet规范场的理解。     

超构透镜的色差调控应用

超构表面是由精心设计和排布的亚波长纳米单元组成的平面元件,其可以在微观尺度下调制电磁场,从而实现波前的任意调控.目前,它已被用来灵活地操纵相位、偏振、振幅等各种光学参数.超构透镜是超构表面中相当重要且非常活跃的一个研究方向,由于其厚度在波长量级,与传统光学透镜相比,能够显著增加光学器件的集成度并且降低结构复杂度.但是,...     

Numerical simulations of negative-index refraction in a lamellar composite with alternating single negative layers

Negative-index refraction is demonstrated in a lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively. Based on the effective medium approximation, simultaneously negative effective permittivity and permeability of such a lamellar composite are obtained theoretically and further proven by full-wave simulations. Consequently, the renowned left-handed metamaterial comprising split ring resonators and wires is interpreted as an analogy of such ENG--MNG layers. In addition, beyond the effective medium approximation, the propagating field squeezed near the ENG/MNG interface is demonstrated to be left-handed surface waves with backward phase velocity.     

Waveguide-resonator coupling structure design in the lithium niobate on insulator for χ((2)) nonlinear applications

The microring resonator based on lithium niobate on insulator(LNOI) is a promising platform for broadband nonlinearity process because of its strong second-order nonlinear coefficients, the capability of dispersion engineering, etc. It is important to control the energy transmitted into the resonator at different wavelengths, as this becomes difficult for two bands across an octave. In this Letter, we study the effect of different pulley bus-resonator configurations on phase mismatching and mode...     

《晶体生长的物理基础》再版发行 序

《晶体生长的物理基础》是闵乃本先生在自己平时讲义基础上逐步完善系统整理而成,是闵先生对晶体生长的理解和研究成果的系统总结,该书首次出版于1982年,是国际上第一本全面论述晶体生长的理论专著,作为高等学校研究生教材或教学参考书,以及从事晶体生长工作的科技人员的进修读物,培养了一代又一代中国材料物理和晶体生长工作者。然而,由于《晶体生长的物理基础》成书较早,闵先生1982年以后在晶体生长方面的诸多理论贡献未能收录其中。本次再版在保持原版体系和特色的基础上,补充了先生生前对原书做的校订和补充,内容比原版更为丰富和系统。祝世宁院士为其亲笔作序,满怀深情追溯了该专著再版的全过程,以及闵院士的杰出贡献和影响。2019年9月16日,闵先生逝世一周年之际,在南京大学举办了《晶体生长的物理基础》再版发行仪式,闵先生的家人、同事、学生、生前好友等出席了仪式。本期特别刊登祝世宁院士为本书所作序言,以及吴以成院士、本刊执行主编彭珍珍在出席仪式上的发言,以表达对先生的深切缅怀和追思!     

光子芯片中相对论引力透镜效应的模拟与光捕获

“光”是自然界中最神秘的物质之一,近代物理学的几次重要革命,都是发源于人们对“光”的探索。爱因斯坦为了描述宇宙时空的本质,建立了广义相对论,其最著名的预言是,光线在天体附近引力场中会发生弯曲(见图1(a))。1919年,天文学家爱丁顿在日食过程中,观测到了太阳引力场中光线的弯曲,直接验证了近代最伟大理论的预言。同样,由于光是世界上速度最快的信息载体,对光的捕获和操控,就像理解光的本质一样,也是人们孜孜不断追求的目标。进入21世纪以来,由于信息技术突飞猛进的发展和光子集成的应用需求,人们越来越需要在微小芯片上操控光子的行为。     

准相位匹配非线性切连科夫倍频与和频效应

研究了两维光学超晶格光波导中的准相位匹配切连科夫(Cerenkov)倍频与和频效应,利用光学超晶格的不同倒格矢实现了多组准相位匹配切连科夫倍频与和频的同时输出,从理论和实验两个方面探讨了光学微结构材料中非线性切连科夫辐射产生的机制、效应和可能的应用.     

Compact surface plasmon amplifier in nonlinear hybrid waveguide

Surface plasmon polariton(SPP), a sub-wavelength surface wave promising for photonic integration, always suffers from the large metallic loss that seriously restricts its practical application. Here, we propose a compact SPP amplifier based on a nonlinear hybrid waveguide(a combination of silver, LiNbO_3, and SiO_2), where a couple of Bragg gratings are introduced in the waveguide to construct a cavity. This special waveguide is demonstrated to support a highly localized SPP-like hybrid mode and a low loss waveguide-like hybrid mode. To provide a large nonlinear gain, a pumping wave input from the LiNbO_3 waveguide is designed to resonate inside the cavity and satisfy the cavity phase matching to fulfill the optical parametric amplification(OPA) of the SPP signal. Proper periods of gratings and the cavity length are chosen to satisfy the impedance matching condition to ensure the high input efficiency of the pump wave from the outside into the cavity. In theoretical calculations, this device demonstrates a high performance in a very compact scheme(~3.32 μm) and a much lower pumping power for OPA compared with single-pass pumping. To obtain a comprehensive insight into this cavity OPA, the influences of the pumping power, cavity length, and the initial phase are discussed in detail.     

Entropy squeezing of the field interacting with a nearly degenerate V-type three-level atom

The position- and momentum-entopic squeezing properties of the optical field in the system of a nearly degenerate three-level atom interacting with a single-mode field are investigated. Calculation results indicate that when the field is initially in the vacuum state, it may lead to squeezing of the position entropy or the momentum entropy of the field if the atom is prepared properly. The effects of initial atomic state and the splitting of the excited levels of the atom on field entropies are discussed in this case. When the initial field is in a coherent state, we find that position-entropy squeezing of the field is present even if the atom is prepared in the ground state. By comparing the variance squeezing and entropy squeezing of the field we confirm that entropy is more sensitive than variance in measuring quantum fluctuations.     

准位相匹配材料研究新进展及应用

准位相匹配材料（光学超晶格）是一种人工非线性光学材料，目前已被广泛应用于倍频，三倍频，光参量振荡等激光变频领域，这种材料可以通过提供倒格矢来满足非线性光学过程中的位相失配，从而提高非线性光学过程转换效率，文章简要回顾了准位相匹配理论的发展过程，对其基本原理及主要应用做了较为详细的描述，并对近年来该领域的一些新进展做了介绍。