Experimental realization of negative refraction and subwavelength imaging for flexural waves in phononic crystal plates

TL;DR

This paper demonstrates negative refraction and subwavelength imaging of flexural waves in phononic crystal plates through a novel thickness contrast design, verified by numerical and experimental methods, enabling tunable elastic lensing.

Contribution

It introduces a new thickness contrast-based phononic crystal design for negative refraction and subwavelength imaging of flexural waves, with experimental validation.

Findings

Negative refraction of flexural waves achieved in phononic crystal plates.

Subwavelength imaging demonstrated experimentally.

Tunable lens focusing achieved by adjusting thickness contrast.

Abstract

In this paper, we numerically and experimentally demonstrate negative refraction of flexural waves in phononic crystal(PC) plates which is employed for designing flat elastic lenses. We propose a thickness contrast-based plate design to achieve refractive index equal to -1 at the interface of the PC and host plate. The thickness contrast between the PC and host plate enables matching their wave numbers in the all angle negative refraction (AANR) frequency regime. The PC-lens design is then numerically and experimentally verified to achieve the image of an omnidirectional subwavelength excitation source. By changing the thickness contrast between the plate and PC, the PC-lens can be tuned for wave focusing and subwavelength imaging at a desired frequency.