Self-referenced temperature sensing with a lithium niobate microdisk resonator

Self-referenced temperature sensing based on thermo-optic birefringence is demonstrated on a Z-cut lithium niobate microdisk resonator. Due to the significant difference between thermo-optic coefficients of ordinary and extraordinary light, quasi-transverse magnetic (quasi-TM) and quasi-transverse electric (quasi-TE) modes in the microdisk show relative cavity resonance shift upon temperature change, which acts as a robust self-reference for temperature sensing. A temperature sensitivity of 0.834 GHz/K and a measurement uncertainty of 0.8 mK are demonstrated with an optical input power of only 1.5 μW.