Miniature temperature sensor based on polymer-packaged silica microfiber resonator

In this study, microfiber knot resonators (MKRs) were fabricated and packaged between two poly-dimethylsiloxane (PDMS) layers in miniature chips. We analyzed their temperature-sensing performance according to the microfiber diameter and ring length. After the rings were encapsulated in PDMS, the temperature sensitivity reached 1.79 nm/°C in the free spectral range (FSR) interval, which was about 10 times higher than that with the bare MKR (187 p.m./°C). The high thermo-optic coefficient of PDMS made the refractive index sensitive to changes in temperature, which affected the transmission spectrum of the MKR structure. The high thermal expansion coefficient of PDMS also deformed the MKR structure. These two factors greatly improved the temperature sensitivity of the MKR sensor. The stable physicochemical properties of PDMS could also enhance the stability of the sensor.