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Plasmon-Assisted Phase-Matched Second- and Third-Harmonic Generation in Single-Negative Heterostructures 下载免费PDF全文
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. 相似文献
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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。 相似文献
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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. 相似文献
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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像。传统光学设计是通过将多片不同色散性质、不同曲面形状的透镜贴合在一起,实现针对几个分立波长的消色差效果,从而可以大致得到比较宽带的近似消色差效果。要实现宽带连续消色差光学元器件始终是一个非常困难的挑战,需要新的设计原理才有可能解决这个问题。 相似文献
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我们研究组长期致力于表面等离激元和超构材料的研究。我们早期提出的实现负折射的耦合渔网结构和偏振调控的L 形单元超构材料都成为了本领域的主流设计方案。在近年来的超构表面研究方面, 我们基于LED芯片实现了偏振调控的动态显示,与澳大利亚国立大学Kivshar教授合作实现超高效率的介质超构表面全息,见图1。近期,我们与台湾蔡定平教授研究组合作,在解决超构表面器件在连续宽频段上消色差的方面取得了重要突破,见图2。我们首先将透镜聚焦所需要的相位分解成两部分,即:频率无关的基础相位和频率相关的补偿相位(与频率成正比)。然后巧妙结合超构表面结构设计的两种方案(共振性和几何相位性),通过几何相位设计聚焦透镜需要的基础相位分布,再通过共振设计补偿不同频率带来的相位色散。需要特别强调的是,通常的共振带来相位变化都是突变的,不满足与频率成正比的线性相位补偿。本项工作中,我们提出了新颖的集成共振(integrate resonance)” 方案,利用特殊排列的金属棒的多个共振之间的线性相位区域,成功设计出满足聚焦透镜要求的一系列不同斜率的线性相位补偿的结构单元(图3(a))。图3(b)显示了利用纳米加工制备的反射性超构透镜样品照片,整个镜片的直径约55 μm,薄膜厚度小于100 nm。右侧电子显微镜照片反映出了该超构透镜的结构单元具有几何相位的旋转排布,以及不同纳米棒形状及数目的集成共振性质。 相似文献
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Effect of thickness variations of lithium niobate on insulator waveguide on the frequency spectrum of spontaneous parametric down-conversion 下载免费PDF全文
Guang-Tai Xue 《中国物理 B》2021,30(11):110313-110313
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. 相似文献
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High-sensitivity Bloch surface wave sensor with Fano resonance in grating-coupled multilayer structures 下载免费PDF全文
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. 相似文献