Soliton microcomb-assisted microring photonic thermometer with ultra-high resolution and broad range

Whispering gallery mode resonators(WGMRs)have proven their advantages in terms of sensitivity and precision in various sensing applications.However,when high precision is pursued,the WGMR demands a high-quality factor usually at the cost of its free spectral range(FSR)and corresponding measurement range.In this article,we propose a high-resolution and wide-range temperature sensor based on chip-scale WGMRs,which utilizes a Si3N4 ring resonator as the sensing element and a MgF2-based microcomb as a broadband frequency reference.By measuring the beatnote signal of the WGM and microcomb,the ultra-high resolution of 58 micro-Kelvin(μK)was obtained.To ensure high resolution and broad range simultaneously,we propose an ambiguity-resolving method based on the gradient of feedback voltage and combine it with a frequency-locking technique.In a proof-of-concept experiment,a wide measurement range of 45 K was demonstrated.Our soliton comb-assisted temperature measurement method offers high-resolution and wide-range capabilities,with promising advance-ments in various sensing applications.