Modeling off-resonant nonlinear-optical cascading in mesoscopic thin films and guest-host molecular systems

A model for off-resonant microscopic cascading of (hyper)polarizabilities is developed using a self-consistent field approach to study mesoscopic systems of nonlinear polarizable atoms and molecules. We find enhancements in the higher-order susceptibilities resulting from geometrical and boundary orientation effects. We include an example of the dependence on excitation beam cross sectional structure and a simplified derivation of the microscopic cascading of the nonlinear-optical response in guest-host systems.

Figure 1

(a) The first-order correction to $f_{zz|i}^{(N-1)}$ for a molecule at the center of a sphere as a function of the lattice vector in the $z$ direction $c$ divided by the lattice vector perpendicular to the field $a$. The inset shows a sphere constructed from a cubic lattice where molecules near the surface have a nonzero $f_{\alpha z|i}^{(N-1)}$ due to surface roughness. (b) The $zz$ component of the first-order approximation to the geometric factor $f_{zz|i}^{(N-1)}$ as a function of depth through the center of a strained $45\times 45\times 45$ cubic lattice (boundaries have zero electric flux).

Figure 2

A vector diagram of the first-order correction to the linear dipole fields for the center layer of a thin film subject to a vertically polarized Gaussian beam. The film thicknesses are (a) 1 layer, (b) 7 layers, (c) 15 layers, and (d) 55 layers of a cubic lattice system with side lengths that extend far beyond the edge of the graphic. Typical relevant line integrals noted in the text are explicitly shown.