Theoretical analysis on spatially structured beam induced mass transport in azo-polymer films.

The radiation force from paraxial beams possessing helical phase fronts causes twists on the surface of an azobenzene polymer sample, and leads to the formation of micro-scale structures. Here, we theoretically investigate the radiation force generated by spatially structured optical beams on a dispersive-absorptive substrate. We derive an analytical expression for the radiation force from spatially structured polarized beams, including, lemon, star, monstar and vector vortex beams in the paraxial regime. Finally, we extend our calculation for non-paraxial beams - optical beams under the tight-focusing regime - and simulate the transverse radiation forces numerically at the focal plane.