一般的波導元件，由於必需滿足全反射的要求，所以中心核的折射率要比包覆層的折射率大。而光在波導中傳遞時，將無法避免掉材料色散的問題，而為了將色散問題減至最低，嘗試利用兩種不同介電質的多層膜做為波導包覆層，使中心核的介質為空氣，進而發展出中空波導。 在此論文中，我們利用半導體製程來完成中空全方向反射鏡波導，此種結構具有低損耗、低材料色散、低極化靈敏度等優點。而更進一步，將其應用在波導分光元件上，用來設計1x8的多模干涉分光器，而較傳統的絕緣層上鍍矽的1x8多模干涉分光器有較好的特性：低損耗、元件尺寸小、極化靈敏度低。 最後，為了改良傳統分光元件，在出口端必須加上彎曲波導以耦合光纖，而造成元件尺寸變大。發展出中空直角波導，除了保有原本中空全方向反射鏡波導的特點，更可適用於取代彎曲波導以縮小元件的面積。 In order to content the total reflection condition in the general waveguide device, the index of core must large than index of cladding layer. It doesn’t avoid the material dispersion. We develop a new waveguide structure with multilayer that has two dielectric materials in different refraction of index to confine light in air core. In this study, we make an omni-directional reflector hollow waveguide with semiconductor fabrication. It has low loss, low material dispersion, and low polarization dependence properties. We applied the structure on the beam splitters to design one by eight multimode interference splitters; it has advantage than conventional silicon-on-insulation structure. Finally, we develop the right angle waveguide to reduce device size that adds the S bend waveguide in device output to couple optical fiber. It keep the advantages of omni-directional reflector and more adaptable than the S bend waveguide in the outputs of multimode interference splitters.
