Scattering of light beams propagating through a dielectric surface with a large-scale roughness: II. Gaussian and non-Gaussian homogenization of scattered beams

The geometric-optic approach is employed to develop an analytical theory of scattering for a normal-incidence light beam with an arbitrary intensity distribution propagating through a dielectric rough plate with a Gaussian statistics and h » λ and l c » λ, where λ is the wavelength of incident radiation and h and l c are the depth and the correlation length of the surface relief. By comparing the results of this analysis with the results obtained in our earlier studies within the framework of scattering theory based on the Kirchhoff method, we determine the applicability ranges of the geometric-optic approach and the phase-screen theory. We will theoretically and experimentally study the homogenization of small-scale (as compared with the beam radius) spatial inhomogeneities of intensity distribution in the cross section of the incident beam in the process of scattering, as well as the transformation of a beam with an arbitrary shape of the cross section into a circularly symmetric Gaussian scattered beam. The class of rough surfaces implementing such transformations is determined. Experiments on a Gaussian homogenization of an astigmatic beam of an excimer ArF laser (λ = 0.193 μm) and a spatially inhomogeneous beam of a multimode Er:YAG laser (λ = 2.94 μm) are performed. The possibility of using the effect of Gaussian homogenization in ophthalmology for laser correction of vision is demonstrated.