Polarization-independent 90°-turns in single-mode micro-waveguides on silicon-on-insulator wafers for telecommunication wavelengths

A theoretical analysis of possible ways to achieve light 90degrees-turns with silicon-on-insulator (SOI) polarization-independent micro-waveguides, which are key elements for telecommunication applications, is presented. Efficiency of various fully-etched corner mirrors and 90degrees-bends has been evaluated for both (well-designed) rib and (square) strip waveguides using three-dimensional finite difference time domain (3D FDTD) simulations. It is shown that SOI rib micro-waveguides which are polarization insensitive have better results with corner mirrors provided that the waveguide height is more that 1.5 mum (loss <0.25 dB), while efficient 90 degrees-turns can be achieved for SOI sub-micrometer strip waveguides using bends provided that curvature radius R is larger than a few microns (loss <0.1 dB for R > 4 mum). In both cases, loss difference between quasi-TE and quasi-TM polarization is estimated to less than 0.04 dB. (C) 2004 Elsevier B.V. All rights reserved.