Ultra‐Low‐Loss Silicon Nitride Photonics Based on Deposited Films Compatible with Foundries

The fabrication processes of silicon nitride (Si3N4) photonic devices used in foundries require low temperature deposition, which typically leads to high propagation losses. Here, it is shown that propagation loss as low as 0.42 dB cm−1 can be achieved using foundry compatible processes by solely reducing waveguide surface roughness. By postprocessing the fabricated devices using rapid thermal anneal (RTA) and furnace anneal, propagation losses down to 0.28 dB cm−1 and 0.06 dB cm−1, respectively, are achieved. These low losses are comparable to the conventional devices using high temperature, high‐stress LPCVD films. The dispersion of the devices is also tuned, and it is proved that these devices can be used for linear and nonlinear applications. Low threshold parametric oscillation, broadband frequency combs, and narrow‐linewidth laser are demonstrated. This work demonstrates the feasibility of scalable photonic systems based on foundries.