Nonlinear self-collimated sound beams in sonic crystals

TL;DR

This paper demonstrates the generation of narrow, non-diverging second harmonic sound beams in a sonic crystal with quadratic nonlinearity, combining analytical predictions and numerical simulations.

Contribution

It introduces a method for producing self-collimated high-intensity sound beams with efficient harmonic generation in sonic crystals.

Findings

Numerical simulations confirm analytical phase matching predictions.

Efficient second harmonic generation occurs with reduced beam divergence.

The study advances control of nonlinear sound propagation in structured media.

Abstract

We report the propagation of high-intensity sound beams in a sonic crystal, under self-collimation or reduced-divergence conditions. The medium is a fluid with elastic quadratic nonlinearity, where the dominating nonlinear effect is harmonic generation. The conditions for the efficient generation of narrow, non-diverging beam of second harmonic are discussed. Numerical simulations are in agreement with the analytical predictions made, based on the linear dispersion characteristics in modulated media and the nonlinear interaction in a quadratic medium under phase matching conditions.