Light-Matter Interaction: Conversion of Optical Energy and Momentum to Mechanical Vibrations and Phonons

TL;DR

This paper explores how light transfers energy and momentum to materials, creating mechanical vibrations and phonons, and examines the mechanisms ensuring conservation laws during light-matter interactions.

Contribution

It provides a detailed analysis of the processes by which electromagnetic momentum is transferred to mechanical vibrations in materials, addressing a key aspect of light-matter interaction.

Findings

Mechanical vibrations carry optical energy and momentum.

Phonons do not carry momentum, affecting energy distribution.

Mechanisms of electromagnetic momentum transfer are clarified.

Abstract

Reflection, refraction, and absorption of light by material media are, in general, accompanied by a transfer of optical energy and momentum to the media. Consequently, the eigen-modes of mechanical vibration (phonons) created in the process must distribute the acquired energy and momentum throughout the material medium. However, unlike photons, phonons do not carry momentum. What happens to the material medium in its interactions with light, therefore, requires careful consideration if the conservation laws are to be upheld. The present paper addresses some of the mechanisms by which the electromagnetic momentum of light is carried away by mechanical vibrations.