Acoustic resonator based on periodically poled transducers: Concept and analysis

Abstract

The demand for highly coupled high quality acoustic wave devices for radio-frequency (RF) signal processing based on passive devices has generated a strong innovative activity, yielding the investigation of new excitation principles and waveguide structures. Periodically poled transducers (PPTs) have been recently investigated [E. Courjon et al., J. Appl. Phys. 102, 114107 (2007)], as an alternative to classical interdigital transducers (IDTs) for the excitation and detection of guided acoustic waves. PPTs have two principal advantages compared to IDTs: the robustness of the excitation versus defects or surface contamination and the possibility to excite waves exhibiting a wavelength equal to the poling period. Here a new acoustic resonator concept is suggested, allowing high frequency operation with a simplified package. The idea consists of using a waveguide based on a PPT fabricated on a ferroelectric single-crystal substrate such as lithium niobate or tantalate inserted between two single-crystal substrates allowing the guidance of elastic waves without losses. The concept analysis points out optimum configurations of the structure allowing the excitation of elastic waves compatible with RF applications.