On chip, high-sensitivity thermal sensor based on high-Q polydimethylsiloxane-coated microresonator

TL;DR

This paper demonstrates a high-sensitivity, on-chip thermal sensor using a PDMS-coated microresonator with high-Q whispering gallery modes, achieving significantly improved sensitivity and resolution over traditional silica sensors.

Contribution

It introduces a novel PDMS-coated microresonator with high-Q modes for enhanced thermal sensing, including a transition in WGM shift behavior and ultra-high resolution capabilities.

Findings

Sensitivity of 0.151 nm/K, ten times higher than pure silica sensors

Transition from red- to blue-shift with increasing PDMS thickness

Thermal resolution reaching 10^-4 K

Abstract

A high-sensitivity thermal sensing is demonstrated by coating a layer of polydimethylsiloxane (PDMS) on the surface of a silica toroidal microresonator on a silicon wafer. Possessing high-Q whispering gallery modes (WGMs), the PDMS-coated microresonator is highly sensitive to the temperature change of the surroundings. We find that, when the PDMS layer becomes thicker, the WGM experiences a transition from red- to blue-shift with temperature increasing due to the negative thermal-optic coefficient of PDMS. The measured sensitivity (0.151 nm/K) is one order of magnitude higher than pure silica microcavity sensors. The ultra-high resolution of the thermal sensor is also analyzed to reach 10-4 K.