The Behaviour of χ$\text{}^{(2)}$ Grating Encoding Function

A new phenomenological model of self-organized second-harmonic generation is proposed describing the photoinduced χ$\text{}^{(2)}$ grating formation as a cumulative third-order nonlinearity via a complex χ$\text{}^{(2)}$ encoding function being dependent upon the light intensities of fundamental and second-harmonic writing radiations. The theoretical results attained are confronted with recent experimental measurements by Lambelet and Feinberg and the χ$\text{}^{(2)}$ encoding function is constructed for this special case.