矽基片B 型抗諧振反射光波導環形共振感測器之設計、製作與其特性量測

Abstract

本論文研究B 型抗諧振反射光波導(ARROW-B)環形共振感測元件。具 有ARROW-B 結構的環形共振感測元件在偵測環境折射率的變化具有很高的 靈敏度特性。此外，由於B 型抗諧振反射光波導擁有較大的導光區，所以能 夠有效和單模光纖相匹配。此感測元件的設計，使用模擬分析光場在元件中 的傳播特性，使其在水環境下具有最佳化的感測靈敏度。利用轉移矩陣法與 等效折射係數法分析與設計B 型抗諧振反射光波導結構。然後，我們利用二 維有限時域差分法模擬B 型抗諧振反射光波導環形共振感測元件的傳波特性 和靈敏度。共設計了四種環形與直波導間隙，分別為0.2、0.4、0.6 及0.8 μm 之元件，模擬得到之靈敏度為298、320、320 及342nm/RIU，另外設計的結 構是在直波導上加覆蓋層(capping layer)，此結構模擬得到之靈敏度為320、 340、320 及320nm/RIU。製作了無覆蓋層的結構並且量測特性。製作的B 型 抗諧振反射光波導環形共振感測元件在間隙是0.4μm 情況下，所量測到的靈 敏度為230.5 nm/RIU。

In this study, ring resonator sensors with antiresonant reflecting optical waveguide of type B (ARROW-B) structures have been investigated. The ARROW-B ring resonator sensor was proposed to provide highly sensitivity characteristics to detect changes in refractive index of the environment. The ARROW-B waveguide with a thick guiding region can provide efficient coupling with a single-mode fiber. Modal characteristics of ARROW-B were analyzed with simulation and designed for obtaining optimum sensitivity in aqueous environment. The characteristics of ARROW-B structure were analyzed with the transfer matrix method and the effective index method. We used the 2D-FDTD (finite-difference time-domain) to simulate the propagation characteristics and sensitivity of the ARROW-B ring resonator sensors. We designed the gap between the ring and the straight waveguide as 0.2, 0.4, 0.6, and 0.8 μm respectively. The simulation sensitivities were about 298, 320, 320, and 342 nm/RIU. We also designed a structure with a capping layer (SiOx) on the bus waveguide. The corresponding simulation sensitivities were about 320, 340, 320, and 320 nm/RIU respectively. The devices without capping layer were fabricated and characterized. The sensitivity of the fabricated ARROW-B ring resonator sensor was obtained as 230.5 nm/RIU for gap 0.4 μm.