# Dispersion free control of hydroelastic waves down to sub-wavelength scale

## TL;DR

This paper demonstrates a novel experimental method to control hydroelastic surface waves at sub-wavelength scales, enabling dispersion-free wave manipulation such as focusing, reflection, and refraction.

## Contribution

It introduces a technique to locally tune the elastic cover properties to achieve dispersion-free control of hydroelastic waves, independent of frequency.

## Key findings

- Achieved broadband focusing, reflection, and refraction of hydroelastic waves.
- Demonstrated a dispersion-free Snell-Descartes law for these waves.
- Explored sub-wavelength wave configurations revealing new surface wave features.

## Abstract

Hydroelastic surface waves propagate at the surface of water covered by a thin elastic sheet and can be directly measured with accurate space and time resolution. We present an experimental approach using hydroelastic waves that allows us to control waves down to the sub-wavelength scale. We tune the wave dispersion relation by varying locally the properties of the elastic cover and we introduce a local index contrast. This index contrast is independent of the frequency leading to a dispersion-free Snell-Descartes law for hydroelastic waves. We then show experimental evidence of broadband focusing, reflection and refraction of the waves. We also investigate the limits of diffraction through the example of a macroscopic analog to optical nanojets, revealing that any sub-wavelength configuration gives access to new features for surface waves.