A bilevel mode converter is analyzed for providing low-loss coupling between the small fundamental mode of a silicon nanowire waveguide and the larger mode of a conventional silicon-on-insulator (SOI) rib waveguide. The bilevel converter can also be used to improve the coupling efficiency between a lensed fiber and a silicon nanowire waveguide. The mode converter consists of two tapers formed at different levels. The top taper comprises a parabolic and sine taper, which is optimized to improve the mode conversion efficiency. Numerical analyses are given by using a three-dimensional semivectorial beam propagation method. The design has good tolerance against misalignment of the two masks needed for the double etch.
© 2006 IEEE
Daoxin Dai, Sailing He, and Hon-Ki Tsang, "Bilevel Mode Converter Between a Silicon Nanowire Waveguide and a Larger Waveguide," J. Lightwave Technol. 24, 2428- (2006)