Spectral dispersion of second molecular hyperpolarizability of diacetylene derivatives: Correlation with electronic and chemical structure

Abstract

Dispersion of the second hyperpolarizability γ(−ω;ω,ω,−ω) of a series of conjugated diacetylene derivatives measured by single beam Z-scan technique, is presented. The spectrum of γ is explained by a three-level model involving a one-photon excited state, a two-photon excited state and the ground state. The location of one and two-photon states and corresponding transition dipole moments have been estimated. The influence of various electronic states on the nonlinear optical properties of these derivatives have been discussed. Broad correlations of the nonlinearity with the structure have been drawn.