Second order nonlinear optical susceptibility of nonelectrically poled DR1-doped PMMA host-guest polymers

Nonlinear optical (NLO) polymers and their applications have been studied for long decades. The fundamental structures of the NLO polymers consist of the host-guest structures; the guest chromophores play a role of nonlinear mixing of multiple waves, while the host polymers fix the positions of the guest. The symmetry of the materials is closely associated with the nonlinear optical susceptibilities. The second order nonlinearity requires the materials to break the centro-symmetry. In general, the NLO polymers exhibit the centro-symmetry in as-prepared conditions, because the guest chromophores are randomly distributed in the host. So-called poling procedure, the procedure applying the DC electric fields, is conducted so as to align the chromophores in the polar order and break the symmetry. In our previous study, we successfully obtain the second order nonlinear susceptibility by using the NLO polymers with the amorphous ferroelectric polymers as host without the conventional poling procedure [1]. Taking advantage of the polarization self-organization behaviors specific to the amorphous ferroelectric polymers, the noncentro-symmetry of the guest chromophores was induced just by annealing the materials at the temperatures higher than the glass transition points (T_g) of the polymers. In the present study, we will report that the nonelectrical poling is available even for the host-guest polymers with poly (methyl methacrylate) (PMMA), one of the most popular host materials for the NLO polymers.