Temporal stability of second-order optical non-linearities depending on non-linear optically active groups of polyesters

Four types of non-linear optical (NLO) polyesters with the same main chain and with different NLO-active groups have been synthesized. Second-order NLO properties of the corona-poled polyesters are studied by the second-harmonic generation (SHG) method. The structure of the NLO-active group affects not only the magnitude of the SHG coefficient (d(33)) but also the temporal stability of d(33). Though all the polyesters show nearly the same glass transition temperature, the polyesters having NLO-active groups with larger dipole moments show better temporal stability, suggesting that the dipole moment has a significant effect on temporal stability.