Surface sum-frequency generation from chiral medium by elliptically polarized light beyond plane-wave approximation and coplanar geometry of incidence

Aiming to study the nonlinear response of the surface of isotropic chiral medium, we obtained analytical expression relating the transverse amplitudes of the spatial Fourier-spectra of two incident arbitrary polarized fundamental beams and one signal reflected beam at the sum-frequency within the first-order approximation by their divergence angles. The calculations, carried out in paraxial approximation, simultaneously take into account the spatial dispersion of the bulk of the medium, its near-surface heterogeneity and the transverse finiteness of the three interacting light beams with arbitrary amplitude profiles and orientation in space. A special compact form for the final formulas was found, which makes use of effective nonlinear transformation tensors, the components of which are solely determined by the geometry of incidence of the beams and the material constants of the medium. A possibility of ``switching off'' the certain mechanisms of nonlinear response by choosing the specific polarization states of the incident beams is discussed.