Research on Silicon-Based Guided-Mode Resonance Devices and Applications

• Main Authors: Che-Lung Hsu, 許哲隆
• Other Authors: 張正陽
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/37161062137632553248

博士 === 國立中央大學 === 光電科學研究所 === 95 === During the past decades, the matured micro fabrication technology has successfully miniaturized the dimensions of optical elements which results in the development of micro-optics. As well, the research of nano-scaled optical elements has also promoted the rapid development of nano-optics in the recent time owing to the wide range of possible applications such as advanced microscopy, high-density data storage, photon manipulation, and even probing techniques that can not achieve in micro-optics. However, the extremely tiny size of nano-optical elements suffers from the strict requirement in fabrication so that the practical application of nano-optics is restricted in a certain degree. Compared with nano-optics, the subwavelength optical elements have raised substantial interests because of their feasible structure and versatile capabilities which should not be approached with micro-optics and make them possessing numerous useful functions such as antireflection surface, artificial dielectrics, polarization sensitive elements, and resonant filters. In this thesis, the guide-mode resonance (GMR) devices which consist of subwavelength diffraction grating and waveguide are developed to possess the functions of optical filters, security recognition, and biosensor. Particularly, we developed the GMR devices with silicon-based materials since that may be potential to integrate with other silicon micro-optical elements. The different resonant structures are constructed such as silicon grating and free-standing silicon-nitride (SiNx) membrane. For the GMR devices developed with silicon grating, first, the quartz is used as the substrate to excite the resonance. We designed the transmission notch filters of flexible bandwidths in the infrared region and then experimentally achieved a wide-bandwidth notch filter of over 150 nm stopband and a band shape of Lorentzian type. To improve the line shape, we utilized the asymmetric binary grating profiles to flatten the stopband effectively. Besides the notch filter, we also proposed a transmission bandpass filter of flattop and wide bandwidth of 200 nm using the asymmetric binary grating profiles which is much less complex compared with the conventional multilayer thin films structure. Furthermore, we proposed an out-of-plane optical filter on a single silicon chip which can be used as a monolithic optical filter on a silicon micro-optical bench. Owing to the strong modulation, i.e. large contrast of refractive index, offered by the silicon grating, the presented GMR devices constructed of silicon are shown to provide with high angular immunity that can significantly decrease the strict demands of precise alignment in GMR device. The use of silicon for optical elements is profitable only in the infrared region. For applications in the visible region, the use of SiNx obviously has more advantages owing to its high transparency in both visible in infrared regions. In addition, to develop the fully silicon-based element, we constructed the GMR devices in a free-standing SiNx membrane suspended on a silicon substrate and used as a transmission notch filter of narrow bandwidth. The proposed structures possess advantages of simple structure, high efficiency, and potential in integrating with other components into a micro-system chip. The methods for tailoring the resonance performance in the unique GMR structure including antireflection grating, spectrum-modifying layer, and cascaded arrangement for stopband flattening are presented. Besides the optical filters, the novel applications of GMR device including security recognition and bio sensing are further developed. First, the SiNx GMR membrane is experimentally demonstrated as an authentication label upon illumination with the unpolarized white light with wide angular tolerances due to the high refractive index of SiNx facilitates the proposed filters possess strongly modulated gratings and immunity for the high angular deviation. The measured reflection resonance has an angular tolerance up to ±5° under normal incidence for the visible region for recognition by human eyes. Afterwards, collaborating with the MOEMS laboratory leading by Prof. Tsung-Hsun Yang, the method for detecting DNA hybridization by utilizing the GMR effect is also proposed by which the resonance wavelength is shifted due to phase change of resonant wave induced from the surface attachment of molecules. Owing to the high sensitivity of resonance effect, the correlations of resonance wavelengths shifted with the length of ssDNA of the hybridizations are demonstrated to successfully detecting the hybridization process.