A subwavelength asymmetric acoustic design for waveform-preserved highly forward transmission

We propose a subwavelength acoustic asymmetric transmission (SAAT) design constituting of a solid-fluid superlattice (SFSL) coupled with an acoustic grating (AG), which can provide waveform-preserved transmission with very high forward transmission and nearly forbidden backward transmission. The unique feature of waveform preservation of the transmission wave is attributed to the low-frequency diffraction characteristics of the AG together with the extraordinary forbidden transmission of SFSL in a broadband frequency range. Both the frequency range and the beam direction of the transmission wave calculated by using finite element method agree perfectly with the analytical predictions. By investigating the influence of several key parameters, including the angular orientation of the AG unit and the periodicity number of the SFSL, we were able to optimize the SAAT device design, which can increase the energy forward transmission up to 60% without waveform distortion, and the reverse transmission is nearly forbidden. Such remarkable features of our SAAT make this design favorable in unidirectional signal transmission applications.