Optomechanical deformation and strain in elastic dielectrics

TL;DR

This paper develops an analytic model to understand how light-induced forces cause deformation in elastic dielectrics, revealing complex nonlinear behaviors and emphasizing the importance of volumetric force considerations over surface momentum changes.

Contribution

It generalizes an analytic approach to model light-induced deformation in elastic dielectrics, incorporating multiple scattering and self-consistent density distributions.

Findings

Deformation exhibits periodic stretching and compression.

Optical trapping is enhanced by deformation effects.

Volumetric forces are essential for accurate force modeling.

Abstract

Light forces induced by scattering and absorption in elastic dielectrics lead to local density modulations and deformations. These perturbations in turn modify light propagation in the medium and generate an intricate nonlinear response. We generalise an analytic approach where light propagation in one-dimensional media of inhomogeneous density is modelled as a result of multiple scattering between polarizable slices. Using the Maxwell stress tensor formalism we compute the local optical forces and iteratively approach self-consistent density distributions where the elastic back-action balances gradient- and scattering forces. For an optically trapped dielectric we derive the nonlinear dependence of trap position, stiffness and total deformation on the object's size and field configuration. Generally trapping is enhanced by deformation, which exhibits a periodic change between stretching and compression. This strongly deviates from qualitative expectations based on the change of photon momentum of light crossing the surface of a dielectric. We conclude that optical forces have to be treated as volumetric forces and that a description using the change of photon momentum at the surface of a medium is inappropriate.