Ultrahigh-Q chalcogenide micro-racetrack resonators

High-quality factor microresonators are an attractive platform for the study of nonlinear photonics, with diverse applications in communications, sensing, and quantum metrology. The characterization of loss mechanisms and nonlinear properties in a microresonator is a necessity for the development of photonic integrated circuits. Here, we demonstrate a high-quality chalcogenide (Ge23Sb7S70) micro-racetrack resonator utilizing Euler curves. The racetrack geometry is studied to minimize loss at both the straight–curved waveguide junction and through the waveguide curve. The material absorption, intrinsic quality factor, and nonlinear index are extracted by a comprehensive model fit to laser wavelength resonance scans. The micro-racetrack resonator possesses a waveguide propagation loss of 8.5 dB/m, an intrinsic quality factor of 4.5 × 106, and nonlinear index of 1.28 × 10–18 m2/W, in a waveguide cross section less than 1 μm2. Our results yield state-of-the-art nonlinear microresonators and establish Ge23Sb7S70 as a low-loss PIC platform.