Characteristics and mechanism of coupling effects in parallel-cladded acoustic waveguides

Abstract

The characteristics and mechanism of coupling effects between parallel cladded acoustic waveguides (PCAWs) are essential when considering their applications in acoustic wave control and signal processing. We investigated its characteristics and revealed the nature of the coupling effect using a theoretical model of two-dimensional PCAWs and simulation experiments. We derived the eigenmode equation describing the behavior of a single waveguide based on the wave acoustic theory and derived analytic expressions for the coupling effects in the PCAWs using the coupled mode theory. Using the finite-element method, we analyzed the waveguide coupling exhibited by this structure given different configurational and acoustic parameter settings. Both theoretical and simulated results indicate that the input wave directed into one of four ports of this structure propagates and tunnels alternately between the two waveguides. Our theoretical model established yields analytic relations between the coupling lengths as well as the dependence on parameters of the evanescent wave and the structure. Analyses indicate wave coupling in the two PCAWs is essentially mediated by the evanescent wave. The unique evolution of the acoustic wave in PCAWs can be employed to develop pure acoustic devices such as frequency-selective filters, directional couplers, and acoustic switches.