整合多模梯形波導之多模干涉矽波導線交錯元件的研究

Abstract

在本論文中，我們使用微型化之多模梯形波導設計出一新穎之多模干涉矽波導交錯結構並且使用時域有限差分法模擬其光學特性。此微型化的梯形波導有效地將入射光場擴束，因此除了降低輸入(輸出)波導與多模干涉波導之間的傳輸損耗，並且減少在波導交錯位置所產生的串音干擾 (Crosstalk)。此外，微型化梯型波導的使用促使縮短於多模干涉波導產生自我成像的所需之距離，進而減小交錯結構所需之多模干涉波導長度少於兩倍的拍長。利用三維時域有限差分法，我們探討不同梯形波導及形狀對於多模干涉交錯結構的特性影響並且獲得一個整合寬度平方變化梯型波導的多模干涉波導交錯結構，其尺寸為5800 × 5800平方奈米，在1550奈米的波長下的插入損耗 為0.15 分貝及串音干擾為 -42分貝，並且擁有於1500奈米到1600奈米波段下的寬頻穿透頻譜。

Novel multimode-interference (MMI)-based crossings integrated with miniaturized tapers are numerically presented for Silicon wire waveguides. These miniature tapers function as field expanders to reduce transition loss between the input/output waveguide and the MMI waveguide and the crosstalk in the crossing region. As a consequence, the lengths of MMI waveguide reduce to less than twice of the beat length. Using finite difference time domain method, we demonstrate that the MMI-based waveguide crossing embedded in the quadratic tapers has the size of 5800×5800 nm2, the insertion loss of 0.15 dB and the crosstalk of -42 dB at the wavelength of 1550 nm and broad transmission spectrum ranging from 1500 nm to 1600 nm.