【作者】 张曦；

【导师】 刘小英；

【作者基本信息】 华中科技大学 ， 光学工程， 2012， 硕士

【摘要】 本论文主要以亚波长光栅为研究对象，分析了其衍射特性及其应用。亚波长光栅的光栅周期远小于入射光波长，只存在零级衍射波，高阶衍射波均为消逝波，因此利用亚波长光栅这种独特的衍射特性可以实现许多传统光学器件无法实现的特殊功能。文中，我们提出了一种结构新颖的亚波长光栅—亚波长高折射率对比度光栅（HighRefractive index Contrast Grating，简称：HRCG）。通过对HRCG结构参数的优化，我们将其设计为偏振分束器，四分之一波片，宽带滤波器和空芯波导。本论文的主要研究工作总结如下：(1)简单介绍了亚波长光栅的衍射特性，并举例说明近年来亚波长光栅的主要应用(2)介绍了光栅的理论研究方法，同时指出亚波长光栅需要采用矢量衍射理论进行分析。由于本论文主要采用严格耦合波理论和等效介质理论对亚波长光栅进行设计，因此我们详细阐述了这两种理论的求解原理。(3)提出了亚波长高折射率对比度光栅，并采用严格耦合波理论分析了它的衍射级次。通过结构参数优化，我们将其设计为偏振分束器。这种偏振分束器在入射光波长为1550nm时，对于TE和TM偏振光同时具有极高的消光比，分别为25583.1和112896.8。(4)介绍了亚波长光栅等效介质理论的二阶近似，并利用这个理论将HRCG设计为四分之一波片。这种四分之一波片在入射光波长为1350~1750nm范围内，对于TE和TM偏振光具有良好的相位延迟特性。(5)引入多层HRCG结构,并将其设计为宽带滤波器。指出多层HRCG结构宽带滤波器的衍射场受多层薄膜结构的干涉效应影响，我们可以利用这种特性来设计和改善此滤波器的滤波性能。我们讨论了HRCG层数和HRCG光栅折射率对于宽带滤波器滤波性能的影响，并设计出了中心波长为1550nm，反射谱线宽为843nm的多层HRCG结构宽带滤波器。(6)介绍了空芯波导的发展状况，并且指出损耗较大是目前所有空芯波导的共同缺点。由于HRCG具有极高的反射率和较宽的反射谱，因此我们可以将其设计为空芯波导。这种空芯波导具有偏振选择性，低阶模损耗低，较宽光谱范围内损耗低等优点。在此基础上，我们还设计了二维HRCG空芯波导，它可以很好地将光波限制在空芯波导内进行传播。更多还原

【Abstract】 This thesis mainly researches subwavelength grating and analyzes the diffractioncharacteristics and applications of it. The grating period of the subwavelength grating is lessthan the wavelength of incident light. As this reason, the subwavelength grating has onlyzero-order diffraction wave and higher order diffraction waves are evanescent wave. We canuse this unique diffraction properties of subwavelength grating to realize many opticalfunctions which can not be achieved by many traditional optical devices.In this thesis, we propose a novel structure subwavelength grating-the subwavelengthhigh refractive index contrast grating (HRCG). We design the HRCG as a polarizing beamsplitter, quarter wave plate and a hollow-core waveguide by optimizing its structuralparameters. The main research work is summarized as follows:(1) The diffraction properties of the subwavelength grating is introduced. The mainapplication of subwavelength grating in recent years is illustrated.(2) The theory researches methods of grating is introduced. It has been pointed out thatthe subwavelength grating needs vector diffraction theory to analyze. This paper uses therigorous coupled-wave theory and effective medium theory to design subwavelength grating.We elaborate on the solving principles of these two theories.(3) A novel subwavelength grating-high refractive index contrast grating is proposed.We use the rigorous coupled-wave theory to analyze its diffraction orders. Through theoptimization of structural parameters, we design the HRCG as a polarizing beam splitter.This polarizing beam splitter has a very high extinction ratio,25583.1and112896.8,respectively for TE and TM polarized light when incident light wavelength is1550nm.(4) Second-order approximation of subwavelength grating effective medium theory isintroduced. We use this theory to design HRCG as quarter wave plate. This quarter waveplate has a good phase delay characteristics for the TE and TM polarized light when theincident light wavelength is in the range of1350~1750nm.(5) The multi-layer HRCG structure is introduced and designed as a broadband filter. Itis pointed out that the diffraction field of the multi-layer HRCG structure broadband filter isinfluenced by the interference effect of the multi-layer film structure. We can use this featureto design and improve the filtering performance of this filter. We discussed the influence of the number of layers and grating the refractive index for the broadband filter filteringperformance. We designed a multi-layer HRCG structure broadband filter of which thecenter wavelength is1550nm and the reflection spectrum width is843nm.(6) The development of hollow-core waveguide is introduced. It has been pointed outthat the large loss is a common drawback for all current hollow-core waveguides. The HRCGhas a high reflectivity and a broad reflection spectrum. We designed it as a hollow-corewaveguide. This hollow-core waveguide has lots of advantages like polarization selectivity,low loss for low order modes, low loss in a wide spectral range. On this basis, we alsodesigned the2D HRCG hollow-core waveguide. It can be well to restrict the light to spreadin the waveguide.更多还原