Super resolution focusing of complex sources above a two-dimensional array of resonators in a three-dimensional environment

Abstract

Time reversal focusing above an array of resonators creates subwavelength features when compared to waves in free space. Previous work has shown the ability to focus acoustic waves near the resonators with and without time reversal with an array placed coplanar with acoustic sources. In this work, a two-dimensional array of resonators is studied with a full three-dimensional aperture of waves in a reverberation chamber. The full impulse response is recorded (including reverberation), and the spatial inverse filter is used to produce a focus among the resonators. Additionally, complex images are produced by extending the spatial inverse filter to create focal images such as dipoles and quadrupoles. Although waves at oblique angles would be expected to degrade the focal quality, it is shown that complex focal images can still be achieved.