Effect of thickness variations of lithium niobate on insulator waveguide on the frequency spectrum of spontaneous parametric down-conversion

We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric down-conversion in the periodically-poled lithium niobate on insulator (LNOI) waveguide. We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum, such as narrowing, broadening, and splitting. We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth. Our study may promote the development of on-chip photon sources in the LNOI platform, as well as opens up a way to engineer photon frequency state.     

基于宽带消色差超构透镜的彩色成像

正研究表明,人类从外界获取的绝大部分信息是通过眼睛得到的。丰富多彩的颜色使我们身边的事物可以彼此区分,也使我们的生活多姿多彩。如何得到对身边彩色世界的最优成像是人们一直以来的终极目标,也是光学研究领域的一个重要课题。然而,我们制造光学元器件的光学材料或多或少存在着色散现象——材料的光学特性随波长变化而改变。这导致了光学元器件的色差现象。色差问题严重影响着宽波段工作的光学系统的精度和效果,特别是在可见光波段的彩色成     

Plasmon-Assisted Phase-Matched Second- and Third-Harmonic Generation in Single-Negative Heterostructures

Dispersion relations of surface plasmon polaritons （SPPs） in sandwiched optical systems are studied. The system is actually a kind of SPP waveguides, with two kinds of single negative material （SNG） as core and cladding layers, respectively. Since both TM and TE polarized SPPs can be excited in the structure, the dispersion of SPPs becomes more abundant and leads to colorful nonlinear opticM properties. The authors demonstrate the effective phase-matched second and third-harmonic generation （SHG, THG） assisted by the coupled SPPs. A cascaded second-order nonlinear process can Mso be achieved in the structure when the thickness of the core layer is properly selected, leading to the simultaneous SHG and THG. Further investigations show that much easier phase-matching can be fulfilled in the SNG waveguide array. Our results would be of potential use for surface-enhanced frequency conversion device such as light emitters or lasers.     

用电阻法研究氧在YBa_2Cu_3O_(7-x)中的扩散

用测量电阻法,在等温条件下在544℃至810℃温区研究了 YBa_2Cu_3O_(7-x)失氧过程中氧的扩散.当T>700℃时扩散激活能为1.47_eV/atom;当 T<700℃时为0.90_eV/atom.两温区的差异可能与氧在四方和正交两种结构中扩散机制不同有关.     

High-sensitivity Bloch surface wave sensor with Fano resonance in grating-coupled multilayer structures

A new type of device consisting of a lithium niobate film coupled with a distributed Bragg reflector (DBR) was theoretically proposed to explore and release Bloch surface waves for applications in sensing and detection. The film and grating made of lithium niobate (LiNbO₃) were placed on both sides of the DBR and a concentrated electromagnetic field was formed at the film layer. By adjusting the spatial incidence angle of the incident light, two detection and analysis modes were obtained, including surface diffraction detection and guided Bloch detection. Surface diffraction detection was used to detect the gas molecule concentrations, while guided Bloch detection was applied for the concentration detection of biomolecule-modulated biological solutions. According to the drift of the Fano curve, the average sensor sensitivities from the analysis of the two modes were 1560 °/RIU and 1161 °/RIU, and the maximum detection sensitivity reached 2320 °/RIU and 2200 °/RIU, respectively. This study revealed the potential application of LiNbO₃ as a tunable material when combined with DBR to construct a new type of biosensor, which offered broad application prospects in Bloch surface wave biosensors.     

铌酸锂晶体及其应用概述

铌酸锂晶体历史悠久,物理效应最为齐全,被用于制备声学滤波器、谐振器、延迟线、电光调制器、电光调Q开关、相位调制器等器件,在电子技术、光通信技术、激光技术等领域得到了广泛应用,并且在第五代无线通信技术、微纳光子学、集成光子学及量子光学等近期快速发展的领域中展示了重要的应用前景.本文简要综述了铌酸锂晶体的基本性质、晶体制备以及应用情况,对铌酸锂晶体未来的应用发展进行了简要分析.     

绿光抽运准周期光学超晶格产生红光与蓝光的研究

使用一块准周期LiTaO3光学超晶格晶体，利用准相位匹配技术，通过光参变产生与和频两个非线性过程，将一束532nm绿色抽运光转变成666nm红光与443nm蓝光。具体过程为，通过参变过程获得红色信号光和红外闲频光，再通过绿色抽运光与红外闲置光和频获得蓝光，两个过程在同一块准周期光学超晶格中实现，准周期超晶格的两个倒易矢量分别补偿这两个过程中的相位失配。抽运光的脉宽为40ps，重复频率为10Hz，在平均功率为0．5mW时，测得红光和蓝光功率分别0．15mW和16．6μW，转换效率达到34％和3％。这一方法，提供了一种用一块超晶格晶体同时获得三原色输出的有效途径。     

基于周期极化LiTaO3晶体的高增益简并啁啾脉冲参量放大

根据准相位匹配理论计算了周期极化LiTaO₃(PPLT)晶体中0类准相位匹配过程(e+e→e)的增益曲线.在此基础上，使用数百μJ的低抽运能量获得了～10⁶的增益和～10.3%的转换效率，实现了中心波长位于1064nm的基于简并光学啁啾脉冲参量放大(OPCPA)技术的高增益放大，为产生超短超强激光脉冲提供了新的技术手段.实验结果与理论预期基本符合.     

多孔硅-Au/Ag枝晶复合材料研究进展

基于金属包裹的多孔硅衬底具有制备成本低、检测能力强的优点。自20世纪表面增强拉曼散射(SERS)现象被发现以来,多孔硅-Au/Ag复合材料逐渐展现出作为SERS衬底的优势,被广泛应用于生物、化学、医疗等领域。本文综述了近些年来基于多孔硅复合Au/Ag纳米颗粒混合平台的研究,重点讨论了将贵金属Ag/Au复合于多孔硅衬底上的制备方法,介绍了它们在不同制备条件下枝晶结构的生长形貌和检测性能,并对多孔硅-Ag/Au枝晶复合结构作为SERS衬底的未来发展进行简要分析。     

繁荣学术,服务产业,正五十,再出发

<正>疫情蔓延却挡不住时代悦动的脉搏,随着2022年新春钟声的敲响,《人工晶体学报》也迎来了创刊50周年。20世纪60年代后期,位于北京郊区的原国家建材局人工晶体研究所为了方便所内技术交流,创办了内部刊物《人工晶体译丛》,主要刊载所内技术人员翻译的国外相关领域最新进展。到1972年,期刊刊登范围逐步扩大,陆续刊出所内研究简报、研究论文等,同时也报道国内相关团队的研究近况,遂更名《人工晶体》。时值我国国防工业建设高潮,与国防工业关系密切的人工晶体材料正取得日新月异的发展,水晶、金刚石、云母三大合成晶体相继研发成功并走向市场,激光晶体、非线性光学晶体、闪烁晶体、压电晶体等一大批晶体合成成功,晶体界急需一本自己的专业期刊方便国内同行的交流。在老一辈晶体专家吴乾章等的共同倡议和努力下,《人工晶体》确定为中国硅酸盐学会晶体生长与材料专业委员会的代表会刊,从此走上时代舞台,肩负起传播中国晶体文化,引领中国晶体科技发展的历史使命。1989年,《人工晶体》更名《人工晶体学报》。