Integrated phononic crystal resonators based on adiabatically-terminated phononic crystal waveguides

In this letter, we demonstrate a new design for integrated phononic crystal (PnC) resonators based on confining acoustic waves in a heterogeneous waveguide-based PnC structure. In this architecture, a PnC waveguide that supports a single mode at the desired resonance frequencies is terminated by two waveguide sections with no propagating mode at those frequencies (i.e., have mode gap). The proposed PnC resonators are designed through combining the spatial-domain and the spatial-frequency domain (i.e., the k-domain) analysis to achieve a smooth mode envelope. This design approach can benefit both membrane-based and surface-acoustic-wave-based architectures by confining the mode spreading in k-domain that leads to improved electromechanical excitation/detection coupling and reduced loss through propagating bulk modes.