Temperature Characteristics of Rayleigh Wave and Leaky Surface Acoustic Wave Propagating in Langasite and its Application in Temperature Sensor

A SAW resonator based on langasite (LGS) substrate with (0°, 138.5°, 116.6°) cut was designed and fabricated. Simulation and experimental results demonstrate that the resonator has two resonance modes, one Rayleigh wave and the other leaky surface acoustic wave (LSAW). The temperature dependent resonance frequencies of both Rayleigh wave and LSAW had been studied. The results show that the turnover temperature of LSAW mode is below absolute zero, namely, the resonance frequency of LSAW changes monotonically in rather wide temperature range, such as from cryogenic to ultrahigh temperatures. Real-time temperature measurement shows that the temperature sensor based on the LSAW mode can effectively monitor the environment temperature, as the thermocouple does. Our work suggests that the LSAW temperature sensor has great application potential in aerospace field for wide temperature range sensing.