An acoustoelectric-induced tailorable coupled resonator surface acoustic waveguide

Here, we introduce a tailorable coupled resonator surface acoustic waveguide (CRSAW), based on a linear defect of elliptical cylinders inside a phononic crystal of ZnO pillars on a Si substrate. The designed elliptical resonators allow the emergence of a minimally dispersive, monomode shear-guiding band inside the local resonance bandgap, owing to their partially broken structural symmetry in comparison with their previously reported counterparts such as pillars and hollow cylinders. Moreover, by introducing reconfigurable waveguide behavior, we benefit from the acoustoelectric-induced elasticity modulation of ZnO, which is a semiconducting piezoelectric material. Switching the conductivity of ZnO structures between two limiting low and high values (0.01 S m-1 and 100 S m-1), a considerable waveguide modulation at full width at half maximum (FWHM) (ΔFWHM = -21%) and guiding frequency (Δfd = -2.81%) are achieved for the designed optimized elliptical cylinder CRSAW while maintaining an acceptable loss value. Benefiting from the proposed ZnO-based elliptical CRSAW, we have achieved simultaneous monomode and low-bandwidth surface acoustic waveguide behaviors, without involving significant fabrication complications. The designed structures open up new horizons toward the realization of promising building blocks for designing reconfigurable and miniaturized SAW RF-filters, demultiplexers, and Mach-Zehnder devices for wireless communications applications.