Low-loss silicon waveguide and an ultrahigh-Q silicon microring resonator in the 2 µm wave band

Silicon photonic-integrated circuits (PICs) operating in the 2 µm wave band are of great interest for spectroscopic sensing, nonlinear optics, and optical communication applications. However, the performance of silicon PICs in this wave band lags far behind the conventional optical communication band (1310/1550 nm). Here we report the realization of a low-loss waveguide and an ultrahigh-Q microring resonator in the 2 µm wave band on a standard 200 mm silicon photonic platform. The single-mode strip waveguide fabricated on a 220 nm-thick silicon device layer has a record-low propagation loss ∼0.2 dB/cm. Based on the low-loss waveguide, we demonstrate an ultrahigh-Q microring resonator with a measured loaded Q-factor as high as 1.1 × 10⁶ and intrinsic Q-factor of 2 × 10⁶, one order of magnitude higher than prior silicon resonators operating in the same wave band. The extinction ratio of the resonator is higher than 22 dB. These high-performance silicon photonic components pave the way for on-chip sensing applications and nonlinear optics in the 2 µm wave band.