RESUMO

We present experimental measurements of light backscattered from double-scale randomly rough surfaces (oceanlike surfaces) with different statistical parameters illuminated at small and large angles of incidence. The surfaces are composed of a small-scale roughness superimposed on a slowly (large-scale) varying surface. The large-scale surfaces are diamond-machined periodic surfaces made on aluminum substrates and have either a sinusoidal or a Stokes wave profile. The small-scale roughness is added with lithographic techniques, and the surfaces are then gold coated. For a linearly polarized incident beam, it is found that the backscattered light is strongly depolarized mainly at small angles of incidence and strong shadowing effects are present for large angles of incidence (θ(inc) > 60°).

RESUMO

We report on the numerical study to model a lensless optical manipulation trap to investigate some observed features as guiding and modulation effects caused by a micro-sphere. For this we calculate the field distribution and force exerted upon a micrometer-sized spherical dielectric particle in an evanescent field. The method of calculation is based on the integral equation formalism describe by A. A. Maradudin, et. al., and A. Mendoza-Suárez and E. R. Méndez. The numerical experiments were done considering a two-dimensional model.

Assuntos

Lentes , Óptica e Fotônica , Análise Numérica Assistida por Computador

RESUMO

We propose and study a numerical procedure for the reconstruction of surface profiles from far-field scattering data. The algorithm, based on wave-front-matching principles, is used to reconstruct one-dimensional surface profiles from amplitude scattering data calculated by using rigorous techniques. The study is complemented by the development of a sampling strategy and considerations of the tolerance of the algorithm to noise in the data.