波導共振模態濾波器的製作與模擬

Abstract

本篇論文主要是在理論及實驗上研究以波導共振模態效應為機制的光學濾波器，此種濾波器主要是由繞射光柵及波導結構構成。在文中會完整討論以光柵繞射理論、等效介質理論、波導理論為基礎的設計原理。我們以GaAs為材料來製作波導共振模態濾波器，因為其具有與其他在GaAs基板上光學元件整合的潛力。元件的製程利用電子束微影及乾蝕刻形成奈米孔洞，而為了讓空氣環繞著光柵薄膜，使用AlGaAs犧牲層的濕蝕刻來完成製作。我們已成功的完成二維波導共振模態濾波器，其中一個濾波器共振峰的反射率峰值為86%於波長1051nm，頻寬為356nm，另一濾波器其共振峰的反射率峰值為91%於波長926nm，頻寬為126nm，我們也驗證了藉由改變光柵週期及填充因子可以調變反射峰的位置及頻寬。最後，我們對於模擬結果與實驗結果做比較與簡短的討論。

In this thesis, the optical filters based on guided-mode-resonance (GMR) effect are studied theoretically and experimentally. These filters are constructed with combined diffraction gratings and waveguide structures. A design rule based on grating diffraction, effective medium method, and waveguide theory is fully discussed. To fabricate the GMR filter, we use GaAs-based materials for their potential in the integration with other optical devices on the GaAs substrate. The device processing includes nano-holes formed by e-beam lithography and dry etch methods. To make the grating membrane surrounding by air, a wet-etch of AlGaAs sacrificing layer completes the fabrication. We demonstrate two 2-D GMR filter successfully. One has a resonance peak at 1051nm with ~86% reflectivity and 356nm bandwidth and, for the other one, the resonance peak of 926nm with ~91% reflectivity and 126nm bandwidth is obtained. We also show that the reflection peaks and bandwidths are variable by tuning the grating periods and fill factors. Finally, a short discussion on the comparison between experimental data and simulation results is presented.