In-situ monitored deposition of SiO2 on longitudinal wave based resonator

Longitudinal leaky surface (LLSAW) waves are interesting in high frequency wideband applications. It has been shown that with coating by SiO₂ overlay the temperature stability of a wave on YZ LiNbO₃ may be improved and useful characteristics can be obtained. In previous publication both theoretical and experimental results were presented on temperature compensation of longitudinal wave by SiO₂ overlay. However, one intriguing feature was the gradual transformation of the longitudinal wave (LLSAW) into a ¿modified¿ LLSAW as the SiO₂ thickness was increased. In this work an attempt has been undertaken to verify the validity of modeling results by in-situ monitoring of the frequency response of a resonator on YZ LiNbO₃ during SiO₂ sputtering. The in-situ monitoring provides a picture of gradual waning of the LLSAW mode and the birth of the ¿modified LLSAW¿ mode. The obtained dispersion data was compared to the modeled dispersion curves. The vanishing of the first mode and the birth of the subsequent mode were clearly observed in the monitored response. The validity of the modeling results has been confirmed. The modeled infinite periodic structure response with coating has been compared to the experimental response of a synchronous resonator. The initial LLSAW and the subsequent ¿modified¿ LLSAW modes predicted in modeling exist, and their change occurs by means of vanishing of the initial mode and the birth of the subsequent mode. The modeling in Comsol Multiphysics correctly predicts the main features of this wave in an almost quantitative way.