Model calculation of the optical susceptibilities taking account of the spatial dispersion of nonlinearity in nonlinear spectroscopy of solutions of chiral molecules

A semiclassical oscillator model, proposed for the interaction of light with complex chiral molecules, takes account of the spatial dispersion of the susceptibility nonlinearity. The components of the macroscopic tensors of the nonlinear optical susceptibilities of the second, third, and fourth order are calculated for an isotropic gyrotropic medium. The calculation is accurate up to terms which are linear in respect of the spatial dispersion parameter and which describe respectively the sum-frequency generation, CARS (ω_a = 2ω – ω₁), and the process ω_b = 3ω – ω₁.