Twenty-nine Million Intrinsic Q-factor Monolithic Microresonators on Thin Film Lithium Niobate

The recent emergence of thin-film lithium niobate (TFLN) has extended thelandscape of integrated photonics. This has been enabled by thecommercialization of TFLN wafers and advanced nanofabrication of TFLN such ashigh-quality dry etching. However, fabrication imperfections still limit thepropagation loss to a few dB/m, restricting the impact of this platform. Here,we demonstrate TFLN microresonators with a record-high intrinsic quality (Q)factor of twenty-nine million, corresponding to an ultra-low propagation lossof 1.3 dB/m. We present spectral analysis and the statistical distribution of Qfactors across different resonator geometries. Our work pushes the fabricationlimits of TFLN photonics to achieve a Q factor within one order of magnitude ofthe material limit.