Band structure and slow waves experimental and theoretical characterization in an high frequency 1D phononic crystal

TL;DR

This study combines experimental heterodyne detected transient grating measurements with simulations to characterize the band structure and slow surface waves in a high-frequency 1D phononic crystal, revealing two band gaps and extremely slow waves.

Contribution

It provides the first experimental measurement of extremely slow surface waves at the band edge in a 1D phononic crystal, validated by finite element simulations.

Findings

Identification of two band gaps in the phononic crystal

Observation of distinct surface wave types

Measurement of extremely slow waves at the band edge

Abstract

We present heterodyne detected transient grating (HD-TG) measurements on 1D surface corrugated Phononic Crystal (PC) with characteristic band edge wave vector of $\pi/5$ $\mu$m$^{-1}$. This experimental investigation enables both the direct band diagram characterization of surface waves and a direct measurement of the group velocity dispersion. The experimental data are compared to the simulations performed with the structural-mechanic module of a finite element method software. In this work we show the presence of two band gaps, observe distinct types of surface waves and, for the first time to our knowledge, measure extremely slow waves in correspondence of the band edge wave vector.