線性及非線性光波導分光元件

Abstract

在光通訊系統被動元件的應用中，利用積體光學方式製作的光波導分光器是很重要的元件之一。由於此類元件在分光角度大的情況下，會有很嚴重的輻射損失(radiation loss)，因此，如何降低光損耗及縮小元件尺寸成為在元件設計上必須克服的困難。本論文中，我們提出低損耗且製程容易的分光器設計，並利用光束傳播法(BPM)來模擬其特性。此外，我們也討論幾種可減少分光損耗的設計架構，並且比較其製程難易度、損耗特性、尺寸大小及設計原理等，其中，微稜鏡(microprism)型的分光元件設計可達到較小尺寸的需求。另一方面，高分子光波導具有低成本、高環境穩定性及製作容易等優點，因此我們利用高分子材料來製作所設計的光波導元件，並提出其製程步驟、參數以及容忍度的分析。為了降低元件封裝時的成本，我們利用簡單的耦光計算來討論封裝時會碰到的問題及光纖與波導對準的技巧。另外，由於高分子材料具有很高的三階非線性係數(third-order nonlinearity)，利用此非線性效應可以製作實用的全光元件，因此我們亦討論非線性光波導的特性及其在分光元件上的應用。

Optical power splitters fabricated by planar lightwave circuit are important in applications for optical communication systems. However, this type of device exhibits a tradeoff between the radiation loss and device compactness. We compare several structures for reducing the radiation loss and discuss the promising microprism-type splitters for compact devices. A simple design with the ease of fabrication and low-loss characteristic is presented with the aid of BPM simulation. On the other hand, polymer optical waveguides can increase the design flexibility with the advantages of low-cost and high environmental stability. We use the BCB polymers for manufacturing the designed waveguide devices. The fabrication procedures as well as tolerances and packaging issues are also discussed. Besides, all-optical devices using the third-order nonlinearity exhibit attractive features. We discuss the basic concept and applications for Y-branch nonlinear waveguide devices.