Phase errors and statistical analysis of silicon-nitride arrayed waveguide gratings

Abstract

We present a statistical analysis of arrayed waveguide gratings (AWGs) in the presence of phase errors in the optical waveguides caused by fabrication process variations. Important figures of merit, such as the insertion loss, crosstalk, and non-uniformity, are parameterized as a function of the coherence length, a physical parameter that characterizes the accumulated phase errors in optical waveguides and that can be extracted by measuring variations in the resonant wavelengths of Mach-Zehnder interferometers. A die-level coherence length of 23.7 mm is measured for sub-micrometer-thick silicon nitride (SiN) waveguides fabricated using a 200-mm wafer process. Through Monte Carlo simulations using a semi-analytical model, we examine the impacts of phase errors on the performance of AWGs with 200 GHz and 100 GHz channel spacings. Our results show that the waveguide phase errors cause remarkable excess insertion loss and crosstalk in an AWG, and also increase non-uniformity across channels.