Subwavelength pulse focusing and perfect absorption in the Maxwell fisheye

TL;DR

This paper demonstrates subwavelength pulse focusing and perfect absorption of flexural waves in a thin plate with a Maxwell fisheye index profile, using a time-reversal shaped sink to achieve efficient energy cancellation and absorption.

Contribution

It introduces an experimental method for achieving perfect wave absorption and subwavelength focusing in elastic media using a tailored sink and time-reversal techniques.

Findings

Subwavelength focusing of flexural waves achieved.

Perfect absorption at the focus point demonstrated.

Sink absorbs energy ten times faster than natural decay.

Abstract

Maxwell's fisheye is a paradigm for an absolute optical instrument with a refractive index deduced from the stereographic projection of a sphere on a plane. We investigate experimentally the dynamics of flexural waves in a thin plate with a thickness varying according to the Maxwell fisheye index profile and a clamped boundary. We demonstrate subwavelength focusing and temporal pulse compression at the image point. This is achieved by introducing a sink emitting a cancelling signal optimally shaped using a time-reversal procedure. Perfect absorption and outward going wave cancellation at the focus point are demonstrated. The time evolution of the kinetic energy stored inside the cavity reveals that the sink absorbs energy out of the plate ten times faster than the natural decay rate.