Abstract
The resolution of acoustic imaging system is restricted by diffraction limit. To beat this limit, early research shows acoustic metamaterials that can manipulate acoustic waves artificially and may act as lens to achieve subwavelength resolution. However, these solutions suffer significant loss therefore lack convincing experimental demonstration. Recent study suggested that arrays of metallic nanorods or nanowire can be used as lens for optical imaging at subwavelength resolution. Similar acoustic hyperlens designs have also been explored, and latest experimental result provided resolution of wavelength/7. Here presented is a holey structured endoscope which supports the transmission of the otherwise-evanescent waves over distances, therefore beating diffraction limit and achieving deep subwavelength imaging. Experimental demonstration shows clear image with feature size of wavelength/50. Such a metamaterial endoscope brings new perspectives to the applications of medical ultrasonography, sonar and ultrasonic non-destructive evaluation.