基於簡單多模干涉結構的小型雙模態切換器

Abstract

本論文所追求的目標是一個模態切換器的尺寸小型化，為了達成這一目標，本研究將調制區塊與元件主要結構整合，在多模干涉結構的兩側進行折射率變化使得模態場型在多模干涉結構中產生偏移，在輸出端達成模態切換的效果，利用這樣的方法可以大幅減少元件的尺寸，在長度方面本論文的元件能夠將以往大於數百微米的模態切換器縮小到只需 38.4 微米，寬度方面則可以降到 3 微米的大小。 在數值模擬方面，本論文設計的是一個雙模態的切換器，針對輸入的 TE0 與 TE1 模態進行切換，為了能夠使元件能夠與半導體製程相符，絕緣上矽 (Silicon On Insulator, SOI) 被選為基板，然後使用商用光學模擬軟體 Lumerical 進行光場在元件中傳播特性的模擬，再配合數學軟體 MATLAB®對模擬所求得的結果進一步分析與匯出數據圖。 在結果的部分，本研究所設計的元件在 1550 奈米光源下，在串擾部分針對 TE0 達到 –15.3803 dB、對 TE1 達到 –17.8115 dB，插入損耗的部分針對 TE0 為 –2.9618 dB、對 TE1 是 –4.2519 dB，頻寬的部分在插入損耗不超過 -4 dB串擾低於 -15 dB的條件下為10 奈米 (1545 奈米 ~ 1555 奈米)，若是與其他的模態切換器做比較，本文的整合型元件能夠將 2700 μm2的尺寸大小縮小到只有 115.2 μm2，也因此成功達成了本研究的元件小型化目標。

The goal of this thesis is to minimize the size of a mode switch. To make this happen, the index modulated regions were applied within both side of the multimode interference region in this design. With this design, the length of the mode switch can be shrunk from hundreds of micrometers down to only 38.4 micrometers and the width can be reduced to 3 micrometers. In this thesis, an SOI (Silicon On Insulator) wafer was used for this two-mode switch which can take advantage of CMOS technology. As for the simulations, the commercial software Lumerical was chosen to simulate the optical propagation in the device and the mathematic software MATLAB® was used to calculate the result of the simulations and generate the result figure for further analysis. The results of this work indicate that the crosstalk for the light signal at 1550 nm is –15.3803 dB and –17.8115 dB for TE0 and TE1, respectively. Meanwhile, the insertion loss is –2.9618 dB and –4.2519 dB for TE0 and TE1, respectively. The bandwidth for the insertion loss not exceeding –4 dB and the crosstalk under –15 dB is 10 nm (1545 nm – 1555 nm). Compared with other active mode switches, the design concept proposed in this thesis can reduce the device size from 2700 μm2 to 115.2 μm2. Thus, the goal for size minimization of the mode switch is successfully achieved in this thesis.