High-sensitivity temperature sensor based on Fano resonance in an optofluidic microcapillary resonator

In this paper we demonstrate a high-sensitivity temperature sensor based on high-order Fano resonance (FR) in an optofluidic microcapillary resonator. High-order FR modes (Q∼3000) are excited in an ethanol-filled optofluidic microcapillary resonator for temperature sensing. Due to the high thermo-optic coefficient of ethanol and a large energy fraction of high-order modes in the core liquid, the sensitivity as high as -0.402nm/^∘C and the detection limit of 0.026°C can be achieved. Also the sensitivity and free spectral range of different order radial modes are calculated theoretically. The experimental results agree well with the theoretical results. Through the comparison between the theoretical and experimental results, the radial order number of the mode used for temperature sensing is estimated to be 10.