We report new advances in Fabry-Perot Bragg grating nanoresonators on low-loss silicon nitride (Si3N4). Building on a previous demonstration of an intrinsic quality factor Qin of 19.3 million with 1.4 dB/m propagation loss, we now achieve Qin up to 121 million on a 100-nm Si3N4 platform with an ultralow propagation loss of 0.19 dB/m. Even on a 300-nm Si3N4 platform, Qin of 58 million is obtained with 0.45 dB/m loss. Crucially, an advanced tapered grating design is introduced to minimize mode mismatch between the waveguide and Bragg mirror. These improvements pave the way for compact ultrahigh-Q photonic integrated resonators for applications in nonlinear optics and precision photonics.
Dagenais et al. (Mon,) studied this question.