Parallel acoustic near-field microscope: A steel slab with a periodic array of slits.

We propose a practical acoustic near-field microscope, which is simply a steel slab with periodic array of subwavelength slits. The near field is transported by the coupling of the incident evanescent waves and the acoustic guided modes supported by the structured slab. The transmission coefficients of the structured slab as a function of the transverse wave vector are theoretically derived, and a theoretical model is employed to study the imaging of the proposed device. Numerical simulations are also performed to verify the theoretical results, which show that subwavelength imaging with good quality can indeed be realized.