Silicon-based cyclic arrayed waveguide grating routers with improved loss uniformity

We present silicon-on-insulator (SOI)-based cyclic arrayed waveguide grating routers (AWGRs) with improved channel loss uniformity in the full free spectral range (FSR) by using dual-tapered auxiliary waveguides between the ends of arrayed waveguides. The field distribution at the image plane of the output free propagation region (FPR) is adjusted by the auxiliary waveguides and a flat-top shape can be obtained by appropriate optimization. 8×8 and 15×15 AWGRs with optimized auxiliary waveguides, having a channel spacing of 3.2 nm and 1.6 nm, respectively, are fabricated and the measured loss non-uniformity is less than 0.5 dB, significantly improved by at least 1.5 dB compared with conventional AWGRs.