Lithium niobate microring with ultra-high Q factor above 108

We demonstrate integrated lithium niobate (LN) microring resonators with Q factors close to the intrinsic material absorption limit of LN. The microrings are fabricated on pristine LN thin-film wafers thinned from bulk via chemo-mechanical etching without ion slicing and etching. A record-high factor up 108 at wavelength 1550 nm is achieved because ultra-smooth interface absence ion-induced lattice damage, indicating an ultra-low waveguide propagation loss ?0.0034?dB/cm. ultra-high will pave way for quantum light source, frequency comb generation, nonlinear optical processes.