In attempts to fabricate
thermally stable second-order nonlinear polymer thin films, we have investigated
the second harmonic generation (SHG) from both nonlinear polymer and guest-host
thin films. We have also investigated the role of capping on the SHG, temporal stability
and relaxation of dipole alignment. Corona poling techniques were employed to orient
the dopants into the noncentrosymmetric structure required to obtain the SHG. The
effect of capping with a polymeric encapsulant below the glass transition temperature
of the polymers on the unpoled and corona poled thin films was studied. Capping
of the nonlinear polymer and guest host thin films have resulted in high SHG with
good temporal stability. SHG signal falls drastically during the first 8 days after
poling while no further significant decay in SHG signal was observed after about
33 days. Our investigations have identified the characteristics required for a good
encapsulant on a non-con-ductive surface.
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