We report taper designs with high transmission efficiencies and with lengths shorter than those needed for adiabatic operation. The tapering occurs between rectangular optical waveguides with the same vertical silicon-on-insulator layer structure, but with different horizontal widths, namely 0.5 and 2.0 µm, and for taper lengths between 0.5 and 3.0 µm. After a comparison between two different optimization methods in a two-dimensional calculation scheme, one of these is repeated using three-dimensional calculations. The results show that, also in the length region where conventional linear and parabolic tapers are not yet adiabatic, tapers with a high efficiency can be designed by applying complex taper structures with more degrees of freedom.
© 2005 IEEE
Bert Luyssaert, Peter Bienstman, Peter Vandersteegen, Pieter Dumon, and Roel Baets, "Efficient Nonadiabatic Planar Waveguide Tapers," J. Lightwave Technol. 23, 2462- (2005)