Wide-range and ultra-low temperature thermometer based on a silicon resonator

In this Letter, the silicon-based microring resonator (MRR) was experimentally demonstrated for cryogenic sensing down to 10 K by overcoming the issue of acquiring the optical signals at low temperatures for on-chip optical sensors. A wide-range temperature sensor from 240 to 10 K was obtained. The experimental results show that the device sensitivity decreased from 64.7 pm/K at 240 K to 4.19 pm/K at 10 K. Theoretical analysis indicates that the reduction in sensitivity is attributed to the weakening of thermo-optic effects with the decrease in temperature, which is well consistent with the experimental results. Based on this work, the silicon-based ring resonators, featuring complementary metal oxide semiconductor (CMOS) compatibility, high-quality factors, and ease of chip-scale integration, are a potential platform for ultra-low temperature monitoring.