Thick waveguides of low-stress stoichiometric silicon nitride on sapphire (SiNOS)

Low-stress stoichiometric silicon nitride (Si3N4) waveguides with an unprecedented thickness of up to 1350 nm and a width in the range of 2.2 - 2.7 µm are fabricated using a single LPCVD step on sapphire substrates (SiNOS). Optical characterization of proof-of-concept ∼1.35 µm thick waveguides show propagation losses in the order of 0.30 ± 0.01 dB/cm at 1600 nm. The proposed process offers a simple route to high confinement Si₃N₄ waveguides, enabling applications in nonlinear and mid-IR integrated photonics.