Sulfur-rich chalcogenide claddings for athermal and high-Q silicon microring resonators

Abstract

Heterogeneous integration of materials with a negative thermo-optic coefficient is a simple and efficient way to compensate the strong detrimental thermal dependence of siliconon-insulator devices. Yet, the list of materials that are both amenable for photonics fabrication and exhibit a negative TOC is very short and often requires sacrificing loss performance. In this work, we demonstrate that As₂₀S₈₀ chalcogenide glass thin-films can be used to compensate silicon thermal effects in microring resonators while retaining excellent loss figures. We present experimental characterization of the glass thin-film and of fabricated hybrid microring resonators at telecommunication wavelengths. Nearly athermal operation is demonstrated for the TM polarization with an absolute minimum measured resonance shift of 5.25 pm · K−1, corresponding to a waveguide effective index thermal dependence of 4.28 × 10−⁶ RIU · K −1. We show that the thermal dependence can be controlled by changing the cladding thickness and a negative thermal dependence is obtained for the TM polarization. All configurations exhibit unprecedented low loss figures with a maximum measured intrinsic quality factor exceeding 3.9 × 10⁵, corresponding to waveguide propagation loss of 1.37 dB · cm−1. A value of−4.75 ± 0.75 × 10−⁵ RIU · K−1 is measured for the thermo-optic coefficient of As₂₀S₈₀ thinfilms.