Negative refraction of acoustic waves in two-dimensional sonic crystals

Abstract

Negative refractions of acoustic waves in a two-dimensional (2D) sonic crystal were studied both experimentally and theoretically. By calculating the acoustic band structure and equifrequency surfaces, we theoretically analyzed the acoustic single-beam negative refraction in the first band operating in the ultrasonic regime. A 2D square sonic crystal was constructed with $2.0\text{\ensuremath{-}}\mathrm{mm}\text{\ensuremath{-}}\mathrm{diam}$ steel cylinders arranged as square arrays of $2.5\phantom{\rule{0.3em}{0ex}}\mathrm{mm}$ lattice constant. A scanning transmission measurement of spatial distribution was carried out to establish the acoustic refraction of a single Gaussian beam. It was demonstrated that the negative refraction is strongly dependent on both frequencies and incident angles, which shows great potential in acoustic devices.