波導光柵在特定條件下，會產生波導模態共振，這種現象造成繞射效率會急遽的變化。利用這種特性可以設計出許多光學元件，諸如偏振器、濾波器等。傳統的方法是利用對稱型波導光柵及薄層的多層相互堆疊，達到單層對稱結構無法做到的共振效應。本論文提出新的設計結構─單層多折射率非對稱型波導光柵，這種結構是在一個周期中，置入超過兩種折射率且填充因子也跟著變化，利用這種結構，可以設計出達到多層波導光柵同樣的效應，且能大幅減低堆疊的層數，提供更簡便的設計和製程方法。Guided-mode resonance (GMR) effect occurring in waveguide grating causes the dramatic change of diffraction efficiency under particular conditions. It finds applications to the optical devices, such as filters and polarizers. Typically, GMR phenomenon cannot be realized by using single-layer grating, but can be realized in the structure consisting of a symmetrical waveguide gratings and thin-film layers. In this paper, we design a new type of optical filters. The structure uses only single asymmetric waveguide grating, without thin-film layers. The asymmetric waveguide is formed by periodically arranging more than two kinds of dielectric materials. This new type of filters can achieve the same effects as in the traditionally designed multilayer structures. In addition, they have the advantages of more compact sizes and are easier to be fabricated.
