Abstract
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.
Highlights
Polymers as optoelectronic materials have been widely studied [1]-[7]
To fabricate thermally stable organic nonlinear polymers (NLP) thin films, we have investigated the role of capping on second harmonic generation (SHG) for [pdcv-ipdi], DEMI-PMMA and TEA (TCNQ)2-PMMA and a more detailed study of temporal stability and relaxation with time for [pdcv-ipdi] was carried out
The nonlinear optical (NLO) properties of the polymer [pdcv-ipdi], with and without capping were studied by in-situ corona poling
Summary
Polymers as optoelectronic materials have been widely studied [1]-[7]. In contrast to crystalline systems, these. To fabricate thermally stable organic NLP thin films, we have investigated the role of capping on SHG for [pdcv-ipdi], DEMI-PMMA and TEA (TCNQ)2-PMMA and a more detailed study of temporal stability and relaxation with time for [pdcv-ipdi] was carried out. We have observed that films deposited on a non-conductive surface experienced several problems and this has been avoided by depositing another polymer layer on the NLP or guest host system by means of spin-coating technique. This layer which we term as the capping layer or encapsulant, protects the nonlinear surface from any physical and chemical changes during in-situ poling and SHG. The in-situ technique developed here allows a characteristic profile to be recorded for each polymer or guesthost film, measuring the SHG as a function of poling field alignment and electric field, and probing the dynamics of the poling and chromophore alignment behaviour
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