矽奈米線波導之微型極化旋轉器元件設計

Compact Polarization Rotators Based on Silicon Nanowire Waveguides

陳奎合(Kuei-Ho Chen)

指導教授 ： 陳瓊華

國立交通大學/電機學院/光電工程系所/碩士(2012年)

https://doi.org/10.6842/NCTU.2012.01033

摘要

在本篇論文中，我們使用矽奈米線波導設計出一新穎之微型極化旋轉器結構並且使用三維有限時域差分法模擬其光學特性。此極化旋轉器之結構為於方正的矽奈米線波導之45方向上放置一正方形氮化矽波導結構，致使獲得兩正交特徵模態為45度線性偏振模態。透過有限元素法計算獲得於波長為1550奈米矽奈米波導之厚度為220奈米時，此氮化矽之結構尺寸為100奈米，其兩最低正交模態之等效折射係數分別為1.558和1.531，而其所對應之半拍長度為28.56微米。鑒於輸入波導與此結構之模態不吻合，我們於結構之前後端皆插入5微米長之錐形波導，透過三維有限時域差分法模擬計算結果顯示此元件之插入損失為0.3dB。此外，在1500奈米到1600奈米波段下的穿透頻譜，其極化消光比超過20dB以上。

關鍵字

矽奈米線波導 ； 極化旋轉器

並列摘要

A novel mode-coupling-based polarization rotator for silicon wire waveguides is presented. This device consists of a Si3N4 nano-waveguides located at one corner of a silicon wire. To obtain two lowest-order eigenmodes with polarization states of 45, the thickness of Si3N4 structure is 100 nm as that of Si layer is 220nm at the wavelength of 1550 nm. The effective indices for these two modes obtained by the finite element method are 1.558 and 1.531, respectively, and then the corresponding half-beat length is 28.56 m. 5-m long tapers are inserted in-between this structure and the input/output waveguide to minimize the coupling loss due to mode mismatch. Simulation results obtained by three-dimensional finite difference time domain method show that this device has the insertion loss of 0.3 dB at the wavelength of 1550 nm, and the polarization extinction ratio of over 20 dB at the wavelength range of 1500 -1600 nm.

並列關鍵字

silicon nanowire waveguide ； polarization rotator

參考文獻

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