以微光纖為基礎之微小環狀共振腔之開發及分析

Abstract

短距離的電訊號傳輸已經有逐漸被光訊號取代的趨勢，短距離傳輸光的波導已可做到微米甚至是奈米尺度，其傳輸損耗為一大關鍵，而表面之粗糙度為決定性之因素。我們研究小組運用傳統抽絲塔之原理，加上改良之抽絲架構，以125微米粗細之光纖為素材做出了一微米以下之微細光纖，且其表面光滑，再藉由鎢針構成之操控工具以及矽晶圓所構成之基底，可以製作出微型之環狀共振腔。由半導體製程的方式，可以做出特定之環型架構，經由PDMS之翻模可得到放置微細光纖之凹槽，藉由適當之工具，我們可以將微細光纖置入其凹槽內。再經由漸減波的方式導光進入微型之環狀共振腔，可以量測到共振腔特有之頻譜，並藉由程式模擬找出其穿透係數、衰減係數以及耦合損耗。其共振頻譜之能量衰減可到達7dB.

We are witnessing a new era that signal transmission in short range is being replaced from electronic ones by optical ones. Optical waveguides for short-range transmission could be made below one micrometer in diameter. The transmission loss is one of the key concerns for practical applications. Among all the loss factors, the surface roughness of the micro or nano waveguide is the major one. Our research group utilized a new fiber drawing process based on the traditional fiber drawing tower to obtain a micro fiber below one micrometer in diameter from a standard single mode fiber. The microfiber inhered smooth surface finish. With proper control by using a tungsten tip to operate over a silicon substrate, a micro ring resonator could be formed. Moreover, taking advantage of lithography process, we could make patterns of photoresist on the silicon wafer. After the molding of PDMS, we could have the patterned PDMS substrate. With such a developed manipulation method, we could put the micro fiber into the patterned slot. Furthermore, we could use the evanescent wave coupling scheme to couple light into the micro ring resonator and measured its transmission spectrum. As compared with existing theories, we could get the transmission coefficient, the round trip attenuation factor and coupling loss of the micro ring . The measured resonance transmission loss was up to 7dB