Broadband Athermal Lithium Niobate Microresonators across C and L Bands

Thin-film lithium niobate holds great promise for developing high-performance integrated photonic devices, but it is susceptible to temperature variation due to its thermo-optic effect and low thermal conductivity. We propose a broadband athermal microresonator in a lithium niobate-titanium dioxide hybrid platform and can flexibly adjust the mode field distributions in different materials to greatly suppress the effective thermo-optical coefficient. The measured temperature-dependent wavelength shift is as low as ±1 pm/K over a wide wavelength range from 1480 nm to 1630 nm. This paves the way for developing thin-film lithium niobate photonic devices with low temperature sensitivity for practical applications.