Integrated Thermal Silica Micro-Resonator Waveguide System With Ultra-Low Fluorescence

Thermally grown silica is one of the most desirable materials for the realization of optical waveguides and whispering-gallery mode micro-resonators due to the ultra-low propagation loss and broad transparency window from UV to mid-IR. Here, we present the design, fabrication, and characterization of a high-Q ring-resonator device with a monolithically integrated evanescent rib waveguide coupler made solely from silica thermally grown on a Si substrate. The device delivered an intrinsic Q-factor of 3.7 × 10
⁶
and operated close to the critical coupling regime for both TE and TM polarizations. The achieved Q-factors were more than three orders of magnitude higher than those of comparable silica resonator devices. Furthermore, we showcase the ultra-low parasitic fluorescence unique to thermally grown silica and compare it to a device fabricated in Si
₃
N
₄
.