High-Resolution Photonic Temperature Measurement System Based on Frequency Locking of Microring Resonator.

In this article, we present a high-resolution temperature measurement method utilizing Pound–Drever–Hall (PDH) frequency locking with a silicon nitride (Si3N4) microring resonator as a photonic thermometer. The temperature response at various intervals demonstrates a measurement resolution of less than 1 mK. Through the calculations of the thermal noise floor and frequency linewidth of the Si3N4 microring resonator, we establish the theoretical resolution limit of the frequency locking method to be $41~\mu \text{K}$ at 1-Hz measurement frequency. This precise and stable temperature measurement technique holds immense potential as an in-situ thermometers for diverse quantum chips, thus accelerating the research progress of chip-level quantum metrology.