Nonreciprocal and dispersive solutions of a magnetoelectroelastic slab waveguide

We apply the transfer-matrix method to the equations of wave motion in a magnetoelectroelastic (MEE) solid and compute the dispersion of an MEE slab waveguide. The dispersion curves exhibit periodic regions of resonance, where the group velocity approaches zero and the mechanical coupling is reinforced. Inside these regions, the group velocity of higher-order modes can slow to 103 - 104 m/s. Substantial nonreciprocity, e.g., a 14.2% difference in phase velocity between forward and backward waves, can be realized within an MEE waveguide at select directions and frequencies. This suggests MEE waveguides as a potential alternative for magnet-free nonreciprocal devices.