Ten-million intrinsic-Q, single-spatial-mode photonic-crystal Fabry–Pérot micro-resonator on thin-film lithium niobate

A photonic-crystal Fabry-Pérot micro-resonator on thin-film lithium niobate (TFLN) achieves milestone intrinsic quality factor up to 5.2×10⁷ with single-spatial-mode resonances. The bending-free, polarization-fixed cavity, integrated with apodized photonic-crystal mirrors, minimizes optical loss and ideally utilizes the nonlinear-optical axis of the material. By employing a wide-core waveguide geometry, the resonator suppresses sidewall scattering to a record-low propagation loss of 0.39 dB/m, approaching the material absorption limit of TFLN.