New acoustic resonator based on periodically poled transducer in lithium niobate or tantalate

In this paper, we propose a new concept of acoustic resonator based on a waveguide structure. In the telecommunication market, composants used are indeed generally bases on Surface Acoustic Wave (SAW) or Bulk Acoustic Wave (BAW) devices. However, those systems present technological limits as short-circuits between the electrodes of the interdigital transducers (for SAW device) or the precise control of the piezoelectric material thick resonator (for BAW device). We suggest a new concept based on a periodically poled transducer (PPT) in a ferroelectric substrate (LiNbO₃ or LiTaO₃), embedded between two guiding substrates in order to create an acoustic waveguide. Periodically poled transducers have been investigated recently as an alternative to classical inter-digital transducers for the excitation and detection of guided acoustic waves. A resonator operating at 131MHz has been successfully fabricated and used in order to stabilize an oscillator at this frequency. However, the developed resonator presents a significant thermal sensitivity. The following experiments have consisted in studying a Si/thinned PPT layer/Si structure in order to reduce the thermal sensitivity.