Performance improvement for silicon-based arrayed waveguide grating router.

We analyze the impact of aberration on spectral performance of silicon-based arrayed waveguide grating (AWG) router with the conventional design using a constant pitch along the grating circle for the array waveguides near the free propagation region (FPR), and simulation results show that due to existence of large aberration, side lobes occur in spectral responses of peripheral output channels for the center input light while more serious side lobes appear in most output channels within a free spectral range (FSR) for the edge channel input. Therefore, there is a high crosstalk in conventional N × N silicon AWG, which is very detrimental for router applications. In order to address it, a simple design with a constant projected period on a line tangent to the grating at its pole for the array waveguides near the FPR is proposed, and aberrations of all output wavelengths within a FSR are kept at a rather low level both for the center and edge input. Then we fabricate two kinds of AWG routers with the conventional and proposed design respectively on a SOI wafer, and experimental results show that spectral responses of the AWG router with the proposed design are significantly improved compared to those obtained in the conventional design, especially for the edge channel input.