Dai Daoxin, Wang Zhi, Julian Nick, Bowers John E
University of California Santa Barbara, ECE Department, Santa Barbara, CA 93106, USA.
Opt Express. 2010 Dec 20;18(26):27404-15. doi: 10.1364/OE.18.027404.
A new way to make broadband polarizers on silicon-on-insulator (SOI) waveguides is proposed, analyzed and characterized. The characteristics of the eigenmodes in a shallowly-etched SOI ridge optical waveguide are analyzed by using a full-vectorial finite-different method (FV-FDM) mode solver. The theoretical calculation shows that the loss of TE fundamental mode could be made very low while at the same time the TM fundamental mode has very large leakage loss, which is strongly dependent on the trench width. The leakage loss of the TM fundamental mode changes quasi-periodically as the trench width w(tr) varies. The formula of the period ∆w(tr) is given. By utilizing the huge polarization dependent loss of this kind of waveguide, a compact and simple optical polarizer based on a straight waveguide was demonstrated. The polarizer is fabricated on a 700 nm-thick SOI wafer and then characterized by using a free-space optical system. The measured extinction ratio is as high as 25 dB over a 100 nm wavelength range for a 1 mm-long polarizer.
提出、分析并表征了一种在绝缘体上硅（SOI）波导上制作宽带偏振器的新方法。利用全矢量有限差分法（FV-FDM）模式求解器分析了浅蚀刻SOI脊形光波导中本征模的特性。理论计算表明，TE基模的损耗可以做得非常低，而同时TM基模具有非常大的泄漏损耗，这强烈依赖于沟槽宽度。TM基模的泄漏损耗随着沟槽宽度w(tr)的变化呈准周期性变化。给出了周期∆w(tr)的公式。利用这种波导中巨大的偏振相关损耗，展示了一种基于直波导的紧凑且简单的光学偏振器。该偏振器制作在700nm厚的SOI晶片上，然后使用自由空间光学系统进行表征。对于1mm长的偏振器，在100nm波长范围内测得的消光比高达25dB。
