| 摘要: | 近年來，由於微製造技術的成熟，使得傳統光學元件的尺寸成功的微小化，並促成了微小化光學的發展。同樣的，有關奈米尺度下的光學元件的相關研究也促成了奈米光學的快速發展，並衍生出許多以往無法利用微光學實現的應用諸如高階顯微技術、高容量密度資訊儲存技術、光子操控技術、以及探測技術。然而，尺寸過於微小的奈米光學元件在製作上的困難度卻導致了在實際應用面上受到不小的限制。相較於奈米光學，次波長光學元件由於其較容易實現的結構，以及諸多微光學元件所無法實現的特性，像是抗反射面結構、人造介質、極化相關元件以及共振濾波器等等應用而引發了大量的興趣。 在本論文中，我們利用結合了次波長光柵以及波導特性所構成之波導共振模態元件來發展包括光學濾波器、安全識別標章、以及光學偵檢器之光學元件。由於矽基光學元件具有可與其他微光學元件做積體化整合之潛力，我們特別利用矽基材料來發展波導共振模態元件。我們發展的波導共振模態元件包含以矽製作成的共振光柵結構以及在懸浮的氮化矽薄膜上製做的共振結構。 首先，我們利用於石英基板上發展利用矽製作的共振光柵元件。我們利用該結構設計具有不同頻寬之穿透式帶止濾波器，並於紅外光波段得到超過150奈米頻寬與羅倫茲譜線的截止頻帶。為了要改善譜線的形狀，我們利用非對稱的二階光柵結構來使得截止頻帶譜線得以平坦化。除了帶止濾波器，我們也提出利用非對稱的二階光柵結構設計出具有200奈米平坦化帶通頻譜之穿透式帶通濾波器，該結構相較於傳統光學薄膜濾波器的多層結構具有更簡單的結構。我們更進一步的提出可於單一矽晶片上實現的非平面式光學濾波器，該單石矽光學濾波器可應用於矽微光學桌上。由於矽本身的高折射率所導致的強調制特性，利用矽發展出的波導共振模態元件對角度具有相當高的容忍度，在實際應用方面可以避免一般波導共振模態元件所要求的精確的角度校準要求。 利用矽製作的光學元件其應用僅限於紅外光的波段範圍。對於可見光頻譜範圍的應用，氮化矽由於對可見光至紅外波段範圍皆具有高穿透的特性，因此，氮化矽光學元件顯然較矽光學元件具有更多的優點。有鑑於此，為了發展完全以矽基材料製作的光學元件，我們發展出一在懸浮於矽基板上之氮化矽薄膜製作之波導共振模態元件以作為窄頻之穿透式帶止濾波器。我們所提出的這個元件具有結構簡易、效率高、以及具有可與其他元件積體化構成一微小化系統晶片的潛力。其中，利用此懸浮氮化矽薄膜之特殊共振結構所達到頻譜改良之目的包括抗反射光柵的利用、頻譜改良膜層，以及利用串接式結構使得頻譜平坦化的方法皆揭示於其中。 除了光學濾波器的應用外，我們也利用氮化矽薄膜之共振結構發展出安全識別標記以及生化光學偵檢器之應用。首先，我們利用氮化矽之波導模態共振元件展示了在一般非極化之自然光的照射下，具有防偽功能的奈米標章。該元件由於氮化矽本身具有較高折射率所導致的強調制特性，使得元件具有大角度的容忍度。以人眼辨識該標章，其角度容忍度在正射及正負五度的角度內。接著，我們與中央大學光電所楊宗勳教授所主持的微光機電實驗室合作研究，發展出可利用波導模態共振效應檢測生物脫氧核糖核酸雜交過程的實驗方法。當生物分子附著在波導模態共振結構表面時，由於相位差的改變使得共振波長產生飄移的現象。基於共振效應本身所具有的高敏感度，我們發現共振波長的飄移與脫氧核糖核酸雜交過程之間的關係可以成功的被觀測到。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. |
