Transversal structure of a sum-frequency beam generated from the surface of a chiral medium

Abstract

In this work we study sum-frequency generation from the surface of an isotropic chiral medium in arbitrary interaction geometry of the paraxial light beams at fundamental frequencies. The analytical formulae have been deduced completely describing the transversal spatial distribution of the electric field in the light beam at sum-frequency. Even in a zero-order approximation on the divergence angles of the beams the transversal spatial intensity distribution in the signal beam is elliptic Gaussian, and its shape depends only on the geometry of incidence, the transversal dimensions and the frequencies of the fundamental beams. Within the first-order approximation approach, generally, the polarization state of light is distributed inhomogeneously in the reflected signal beam cross section, and the transversal intensity distribution is not Gaussian. But when the fundamental beams are not focused tightly enough, the non-Gaussian part of the field is negligibly small, compared to the Gaussian part with uniform polarization distribution. However, at larger angles of incidence the non-Gaussian contribution becomes comparable with the Gaussian zero-order part of the field (or exceeds it) even in the case of slightly focused fundamental beams. In this case the transversal distributions of intensity and polarization of light become very sophisticated.