Optical Thin Films with Very Low Refractive Index and Their Application in Photonic Devices
Optical Thin Films with Very Low Refractive Index and Their Application in Photonic Devices
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极低折射率光学薄膜及其在光子器件中的应用
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
E. Schubert
中科院分区：
文献类型：
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作者：
J. Xi;J. Kim;D. Ye;J. S. Juneja;T. Lu;Shawn;E. Schubert
介电多层结构、光学谐振器和光子晶体中的折射率对比度是重要的品质因数，这产生了对具有非常低折射率的高质量薄膜的强烈需求。本文采用电子束蒸发法，在85 °的入射角下，制备了折射率n= 1.08的SiO_2纳米棒。扫描电子显微照片揭示了一个高度多孔的柱状结构的低折射率（低n）膜。SiO2纳米棒之间的差距小于50 nm，即比可见光的波长小得多，因此足够小以使散射小到可以忽略。沉积在Si衬底上的低n膜的光学显微照片揭示了没有明显散射的均匀镜面膜。前所未有的低折射率的二氧化硅纳米棒层的椭圆偏振测量和薄膜干涉测量证实。采用SiO2纳米棒层的单对分布布拉格反射器（DBR）具有增强的反射率，显示了低n薄膜在光子结构和器件中的巨大应用潜力
The refractive index contrast in dielectric multilayer structures, optical resonators and photonic crystals is an important figure of merit, which creates a strong demand for high quality thin films with a very low refractive index. SiO2 nano-rod layers with low refractive indices n= 1.08, the lowest ever reported in thin-film materials, is grown by oblique-angle e-beam deposition of nano-rod layer with vapor incident angle thetas = 85deg. Scanning electron micrographs reveal a highly porous columnar structure of the low-refractive-index (low-n) film. The gap between the SiO2 nano-rods is les 50 nm, i.e. much smaller than the wavelength of visible light, and thus sufficiently small to make scattering negligibly small. Optical micrographs of the low-n film deposited on a Si substrate reveal a uniform specular film with no apparent scattering. The unprecedented low index of the SiO2 nano-rod layer is confirmed by both ellipsometry measurements and thin film interference measurements. A single-pair distributed Bragg reflector (DBR) employing the SiO2 nano-rod layer is demonstrated to have enhanced reflectivity, showing the great potential of low-n films for applications in photonic structures and devices