Second harmonic generation in planar samples of ferroelectric liquid crystals

dNon-linear optical properties of ferroelectric liquid crystals are often studied through second harmonic generation measurements on homeotropic cells. However, it is not always possible to prepare well aligned unwound samples in the homeotropic geometry, especially when dealing with photopolymers or tightly twisted SmC* materials. Here we analyse the problem of extracting the second order susceptibility coefficients d(ij) from second harmonic generation measurements performed on planar samples. Several experimental configurations of polarizer, sample and analyser dispositions are proposed to deduce the complete d(ij) tensor together with the dispersion of the refractive indices and the birefringence both at the fundamental and second harmonic frequencies, Measurements carried out on planar and homeotropic cells for a classical non-linear optical material(W314) are presented and the resulting d(ij) coefficients are compared.