Acoustic Fresnel lenses with extraordinary transmission

We investigate numerically and experimentally highly efficient acoustic lenses based on the principle of extraordinary acoustic transmission. We study circular, flat lenses composed of perforated air channels. The geometry is similar to binary Fresnel lenses, and the lenses exploit several resonance mechanisms to enhance the transmission, such as Fabry–Perot resonances in the channels and cavity resonances on the lens surface. The proposed lenses are able to transmit up to 83% of the incident energy and generate sharp focusing with very high amplification (up to 16 dB experimentally). Furthermore, the resulting lenses are thinner than other designs providing similar performance, making them ideal candidates for application in acoustic imaging and medical diagnostics