Athermal and High‑Q Hybrid TiO2–Si3N4 Ring Resonator via an Etching-Free Fabrication Technique

In this work, we have demonstrated a hybrid TiO2–Si3N4 ring resonator with a high-Q and a temperature-insensitive resonance. The waveguide consists of a thermo-optic positive Si3N4 slab and a negative TiO2 overcladding. The TiO2 layer has a shallow ridge structure, which has been designed to realize an athermal operation and maintain a low scattering loss. During the fabrication of this waveguide, there was no need to utilize the dry-etching process. The method affords a straightforward fabrication and a precise control over the waveguide dimensions. As a result, the ring resonator exhibits a high Q value of 1.55 × 105, a low propagation loss of 0.4 dB/cm, and a small temperature-dependent wavelength shift of 0.14 pm/°C between 25 and 60 °C.