Calculation of the optical force on an infinite cylinder with arbitrary cross section by the boundary element method

We have developed and implemented a numerical scheme to compute optical forces in two-dimensional (2D) structures based on the boundary integral equations, which are solved by the numerical boundary element method. We demonstrate the efficiency of this method by calculating the optical scattering and radiation pressures exerted on 2D objects under the illumination of both plane wave and cylindrical Gaussian beams. The results are validated by comparing to analytical Mie scattering results on circular cylinders. In the framework of this approach the object can be of arbitrary shape with dimensions either far larger, comparable, or much less than the wavelength concerned, and the constituent components can be either dielectric or metallic. We applied the method to study the resonance enhancement of optical forces and the effect of surface roughness on such enhancement. Surprisingly, we found that a cylinder with "controlled roughness" can give a stronger optical force than a smooth surface at resonance.