Ultrahigh Sensitivity Temperature Sensor Based on Harmonic Vernier Effect

A high-sensitivity and miniature open cavity Fabry–Perot interferometer (OCFPI) encapsulated with the polydimethylsiloxane (PDMS) film based on high-order harmonic Vernier effect is designed experimentally investigated. To best of our knowledge, PDMS applied for first time to fill OCFPI obtain high-temperature sensitivity. The resonant dip (peak) wavelength temperature sensor monotonically moves toward shortwave direction as increases from 40 °C $60~^{\circ }\text{C}$ due effects expansion thermo-optic property PDMS. proposed provides following excellent performance advantages: 1) compared traditional all-fiber air-cavity OCFPIs sensitivity approximately 10 pm/°C, has a much higher −3.4 nm/°C at range notation="LaTeX">$40~^{\circ – magnification factor ( notation="LaTeX">${M}$ -factor) 11 when order notation="LaTeX">${i} =4$ ; 2) exhibits good reversibility during heating cooling processes, measured -factor matches well theoretically calculated -factor; 3) shows stability maximum deviation 0.567 nm (internal envelope fourth-order effect) 0.042 (upper envelope) within 450 min; 4) inexpensive, robust, easy fabricate, compact, which can be used in harsh environments. Therefore, it potential dynamic measurement.