Macroscopic view of light pressure on continuous medium

TL;DR

This paper clarifies the macroscopic description of light pressure on continuous media, proposing a unified, simple formulation compatible with polariton momentum and applicable to various light-matter interactions.

Contribution

It introduces a consistent form of the macroscopic field stress tensor that unifies pressure descriptions across different light-matter interactions.

Findings

Proposes a unified stress tensor for light pressure.

Compatible with polariton momentum $ k$.

Generalizes Rytov's electromagnetic momentum density.

Abstract

The ambiguity of macroscopic description of light pressure on continuous medium originates from the uncertainty of dividing the energy-momentum tensor of electromagnetically excited matter into material and field parts or, equivalently, the total acting force into pressure and deformation terms. We show that although there exists a continuum of formally correct formulations, one can adopt the appropriate form of the macroscopic field stress tensor that allows unified description of pressure during elementary light-matter interactions, such as reflection/refraction, absorption and nonlinear conversion. The proposed expressions for the pressure force are simple, convenient and compatible with the polariton momentum $\hbar \bf k$. The corresponding electromagnetic momentum density (14) generalizes Rytov's definition for right-handed and left-handed frequency dispersive media.