Simultaneous unidirectional reciprocal filters of electromagnetic and elastic waves based on the modal symmetry of phoxonic crystal waveguides and cavity

We theoretically achieve the simultaneous unidirectional reciprocal filter of electromagnetic (EM) and elastic waves in a single phoxonic crystal by the finite-element method. The functionality is achieved by matching and mismatching the modal symmetry between a resonant cavity and two mutually perpendicular waveguides. Suitable phoxonic cavity and waveguides are created to realize the match and mismatch of the modal symmetry for both EM and elastic waves. The proposed device has the abilities of phoxonic unidirectional filtering as well as providing great potential for enhancing acousto-optic coupling by simultaneously tailoring electromagnetic and elastic waves with an ultracompact footprint size.