Phononic High Harmonic Generation

TL;DR

This paper provides experimental evidence of phononic high harmonic generation, demonstrating a cascade process triggered by a threshold instability in driven phonon modes, which could be relevant to other physical systems.

Contribution

It introduces the first experimental demonstration of phononic high harmonic generation via a threshold-dependent instability mechanism.

Findings

Observation of cascade harmonic generation in phonons

Identification of threshold-dependent phononic instability

Evidence of high-order harmonic conversion

Abstract

This paper reports experimental evidence for phononic low-order to high-order harmonic conversion leading to high harmonic generation. Phononic high harmonic generation is mediated by a threshold dependent instability of a driven phonon mode. Once the threshold for instability is met, a cascade of harmonic generation processes is triggered. Firstly, the up-conversion of first harmonic phonons into second harmonic phonons is established. Subsequently, the down-conversion of second harmonic phonons into first harmonic phonons and conversion of first and second harmonic phonons into third harmonic phonons occur. On the similar lines, an eventual conversion of third harmonic phonons to high orders is also observed to commence. This physical pathway for phononic low-order to high-order harmonic conversion may find general relevance to other physical systems.