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Compact acoustic metalens with sinusoidal sub-channels for directional far-field sound beams

A metasurface lens (i.e., metalens), composed of perforated sinusoidal channels evenly arrayed with sub-wavelength distances, is explored in this paper. Enhanced directional far-field sound transmission over a large frequency range was realized through using this compact metalens. Numerical simulations and experimental tests demonstrated a pronounced diffraction-limited sound beam from 7390 to 7600 Hz, which reached as far as 57.6 cm at 7551 Hz with a width of 9 cm. This metalens is a feasible candidate for directional sound projection and sound energy harvesting.