Nonlinear optical properties and poling dynamics of a side-chain polyimide/disperse-red dye film: in situ optical second-harmonic generation study

Nonlinear optical (NLO) polymers are advantageous over inorganic crystalline materials in several aspects and have found interesting applications such as modulators, switches, and more recently as photorefractive devices. However, the second-order NLO response of the materials, which is created by an electric poling process, decays as time lapses. For the use of an electrooptic device, it is highly desirable to keep the NLO response in an infinitely long period. But for the photorefractive applications, a fast response of the orientational distribution of NLO molecules to an electric field is more important. For both cases, the orientational distribution and its response to an electric field convey valuable information of the polymeric materials. In this report, the authors show that probing the orientational distribution of NLO molecules during the poling process provides insight of the thermal stability of the NLO response and the underlying interaction between the polymer and NLO molecules