使用奈米壓印的聚合物覆SOI光柵耦合器之設計

Abstract

奈米壓印是一種逐漸被重視的微影技術，透過模板便可以將所設計的圖形壓印在基板上，近年來已被運用在於硬碟、顯示器以及太陽能電池的製作。在耦合技術中，垂直耦合透過其可以改變入射光波向量的特性，可以由各個角度入射耦合而不被波導行進方向所束縛。垂直耦合運用最多的便是光柵耦合器，但是光柵耦合器傳統的製程需要利用浸潤式微影或是電子束微影，必須花上較大的成本與較多的時間。然而透過採用奈米壓印的製程，便可以大幅改善浸潤式微影與電子束微影需要的成本。本論文利用數值模擬的方法來設計光柵耦合器，透過在SOI平台上設計聚合物光柵，完成對1550奈米波長有57.2% 耦合效率的光柵耦合器，以及88%模態間的相似。接著，透過最佳化來改變各個光柵的結構參數，設計出有67.4%耦合效率、97%模態間相似的光柵耦合器，透過反射層的使用可以使耦合效率再上升至84.8%，設計出透過奈米壓印製程的高效光柵耦合器。

Nanoimprint lithography which is patterned by mold is favorable for the process of hard disk drive, displays, and solar cells. Within coupling techniques, the vertical coupling can modify k-vector of the incident light, permitting light not to couple from lateral sides of waveguide. The most generally adopted in vertical coupling is the grating coupler. The traditional process of grating coupler needs immersion lithography or electron beam lithography which costs more expense and time. This problem can be improved by utilizing nanoimprint lithography. In this thesis, we use numerical simulation to design a grating coupler. The proposed grating coupler is based on nanoimprint lithography on SOI platform and it can reach coupling efficiency of 57.2% and modal overlap of 88% at the wavelength of 1550 nm. By optimizing the parameter of each grating, the grating coupler can accomplish coupling efficiency of 67.4% and modal overlap of 97%. By including a bottom reflector, the grating coupler achieves high coupling efficiency of 84.4%. The high-efficiency grating coupler can be designed by nanoimprint lithography process.