Nonlinear optical properties and chromophore electrostatic interactions for the poly(ether ketone) guest-host polymer films

The poly(ether ketone) (PEK-c) guest-host system thin films doped with diff erent weight percents of 3-(1,1-dicyanothenyl)-1-phenyl-4,5-dihydro-1H-prya zole (DCNP) were prepared. Their second-order nonlinear optical (NLO) coeff icients chi ((2))(33) were measured by using the Maker fringe method throug h in-situ second-harmonic-generation (SHG) probing. Experimental results in dicated that, at high chromophore loading in the polymer system, the second -order NLO properties of the poled polymer films could decrease with increa sing chromophore loading. In this paper, the relationship between the macro scopic second-order NLO coefficient and the chromophore number density was investigated by considering the role of the electrostatic interactions of c hromophores in the polymer films. According to the improved relationship, t he macroscopic second-order NLO coefficient is no longer in a direct ratio with the chromophore number density in the polymer films, especially when t he chromophore loading is high. The effect of the electrostatic interaction s of chromophores on second-order NLO properties was discussed from the imp roved relationship.