Ultrahigh-sensitivity temperature sensor based on an elastic TPU capillary whispering gallery resonator

An ultrahigh sensitivity temperature sensor based on an elastic thermoplastic urethane (TPU) capillary whispering-gallery mode (WGM) microcavity is proposed. The temperature sensor comprises a dye-doped TPU capillary and two sealed fused silica capillaries covered at both ends and is fabricated via a thin film assembly and wet etching. The fused silica capillaries limit the thermal volume expansion of the air within it. The volume of the exposed part of the elastic TPU capillary, which has an ultrahigh sensitivity to temperature compared with the thermal volume expansion of material, is increased; the designed elastic TPU capillary WGM microcavity exhibited an ultrahigh sensitivity of 11.28 nm/°C.