Whispering-Gallery-Mode Optical Microshell Resonator Infrared Detector

We demonstrate a thermal infrared (IR) detector based on a high quality-factor (Q) whispering gallery mode (WGM) borosilicate glass microspherical shell resonator and investigate its performance to detect IR radiation in 1 - 20 mu m wavelength range. The resonator exhibits a temperature sensitivity of 1.17 GHz/K with a Q-factor of 3 million and can be configured as a high sensitivity infrared sensor. The microspherical shell IR sensor exhibited a responsivity of 7.88 kHz/nW and achieved a noise-equivalent-power (NEP) of 19 nW/root Hz experimentally. A laser Doppler vibrometer (LDV) is used to measure the physical expansion of the microspherical glass resonator when IR radiation is absorbed. Based on the experimentally measured diametric expansion of the shell per unit IR power absorbed, the NEP of 19 nW/root Hz corresponds to a dimensional change of 2 pm which can be resolved using the resonator. Using COMSOL modeling, thermal expansion analysis was performed for the absorbed IR Power. Using these values of dimension change of the microspherical shell, the dependence of resonance frequency shift on absorbed IR power was simulated. These models show that a NEP of 690 pW/root Hz can be achieved for the microspherical shell with a diameter of 2 mm and a thickness of 2 mu m.

Automated summary

Researchers demonstrated a thermal infrared detector based on a high quality-factor whispering gallery mode borosilicate glass microspherical shell resonator, which showed high sensitivity and temperature sensitivity. The experimental results showed excellent performance of the infrared sensor in the 1-20 μm wavelength range, with high noise-equivalent-power and responsivity, allowing for nanoscale measurements.