Compact Arrayed Waveguide Gratings Fabricated on 800-nm-Thick Si3N4 Photonic Integration Platform

Silicon nitride (Si₃N₄) waveguide with thickness of >600 nm having strong mode confinement and anomalous group velocity dispersion (GVD) has today become the leading photonic integration platform for linear and Kerr nonlinear photonics. However, due to the significant stress issue encountered in the deposition of thick Si₃N₄ film, there is a stringent requirement on the Si₃N₄ region with no etching. Hence it is very challenging to fabricate an arrayed waveguide grating (AWG) which has large potential applications for high-density integrated optical interconnect systems and on-chip filters (e.g., separate optical frequency comb signals), on the thick Si₃N₄ platform because of its large free propagation region (FPR). Here, for the first time to the best of our knowledge, we demonstrate an 8 × 8 100 GHz spacing AWG router and a 6 × 6 200 GHz spacing AWG multi/demultiplexer on the 800-nm-thick Si₃N₄ platform using a standard multi-project wafer (MPW) foundry process, by optimizing structural parameters. Both AWGs exhibit good performance with on-chip loss of ∼1.2 dB and small channel wavelength deviation of <0.04 nm over their respective mean wavelengths. The measured adjacent channel crosstalks are <−19.1 dB and −23.7 dB, and the non-adjacent channel crosstalks are <−15.5 dB and −18.3 dB, for the 100 GHz and 200 GHz AWGs, respectively. The higher non-adjacent crosstalk is mainly due to the currently employed mask grid snapping size of 5 nm during mask generation, and by simulation it can be substantially decreased, e.g., by ∼17 dB through utilizing a finer grid snapping size of 1 nm.