Effect of Bragg Acoustic Reflector on Thermal Processes in SMR under High Power Levels

The paper discusses the thermal processes in solidly mounted resonators with various types of a Bragg acoustic reflector. For modeling temperature distribution in the structure of the resonator, the 2D analytical model is used. The structure of the resonator is divided into seven regions. The region of the Bragg acoustic reflector is substituted by equivalent structure for which the equivalent thickness and thermal conductivity are determined. The parameters of other regions correspond directly to the ones of the resonator layers. For all regions, the stationary heat conduction equation and the corresponding boundary conditions are established. The solution of the heat equation is carried out by analytical method. Using this approach the overheating temperature distributions in the solidly mounted resonators consisting of a thin-film piezoelectric transducer based on AlN or ZnO layer and Bragg acoustic reflector based on 5 pair of Al-Mo or SiO2-Mo layers, were determined. Also the dependencies of the specific power generated in piezoelectric layer and the weighted average overheating temperature of this layer in the resonators with the various reflectors on the resonance frequency were found.