High-Q tellurium-oxide-coated silicon nitride microring resonators.

We report on tellurium-oxide (TeO₂)-coated silicon nitride microring resonators with internal quality factors up to 7.3×10⁵, corresponding to 0.5 dB/cm waveguide loss, at wavelengths around 1550 nm. The microring resonators are fabricated using a silicon nitride foundry process followed by TeO₂ coating deposition in a single post-processing step. The silicon nitride strip height of 0.2 μm enables a small microring bending radius, while the TeO₂ coating thickness of 0.33 μm results in a large modal overlap with the TeO₂ layer. These results are a promising step towards realizing compact and high-performance linear, nonlinear, and rare-earth-doped active integrated photonic devices with this platform.