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.
Highlights
When a wave is inputted into one of four ports of a pair of parallel cladded waveguides, the wave propagates and tunnels alternately between the pair waveguides rather than being confined to propagate along the original incident waveguide
Sun and colleagues analyzed the wave coupling between two parallel phononic crystal waveguides and evaluated the coupling length (CL) using numerical experiments [26]; here, CL is defined as the propagation distance necessary for an acoustic wave to transfer from an initial waveguide to an adjacent waveguide
Applying the wave acoustic theory, we presented the propagation characteristics of acoustic waves in both the cladding and core zones of a single cladded acoustic waveguides (CAWs) by imposing appropriate continuous boundary conditions
Summary
When a wave is inputted into one of four ports of a pair of parallel cladded waveguides, the wave propagates and tunnels alternately between the pair waveguides rather than being confined to propagate along the original incident waveguide. We studied the waveguide coupling in a structure of three parallel ducts and found that CL for two adjacent waveguides solely depends on the wave frequency and the spacing between the two cores but independent of the input mode [37]. The above studies demonstrated the phenomena and applications of waveguide coupling in the CAWs, but little is known of its mechanism and characteristics of the coupling effect from a theoretical point of view. We present a detailed theoretical model of waveguide coupling and reveal the mechanism and the characteristics of the coupling effects in two-dimensional parallel CAWs (PCAWs). To verify theoretical results, the finite-element simulation is used to demonstrate and analyze waveguide coupling phenomena in the PCAWs for different core spacings and frequencies. The theoretical model may serve in applications of waveguide coupling to acoustic wave regulation and signal processing
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