Light forces induced by scattering and absorption in elastic dielectrics lead to strain inducing local density modulations and deformations. These perturbations in turn modify the light propagation 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 finite 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 even allowing areas of bistability. This strongly deviates from qualitative expectations based on the change of photon momentum of light crossing the surface of a dielectric.

Date Published: 10 October 2012
PDF: 9 pages
Proc. SPIE 8458, Optical Trapping and Optical Micromanipulation IX, 84581Z (10 October 2012); doi: 10.1117/12.2000309

Published in SPIE Proceedings Vol. 8458:
Optical Trapping and Optical Micromanipulation IX
Kishan Dholakia; Gabriel C. Spalding, Editor(s)