Improved optical nonlinearity of poled stilbene doped polymer films

The optical properties of corona poled 4'-N,N-dimethylamino-nitrostilbene ( DANS) and a newly synthesized alpha'-cyano-4'-nitro-4-N,N-dimethylaminostil bene (CNDS) doped poly(methyl methacrylate) (PMMA) film were investigated w ith in situ second-harmonic generation (SHG) measurement and absorption mea surement. Optimum corona poling temperatures of these polymer films were fo und to be lower than glass transition temperatures of the materials, most p robably due to the dramatic increased conductivity of the films and phase s eparation. Under the optimum: corona poling condition, the alignment orderi ng of CNDS was lower than that of DANS from the absorbance before and after : corona poling. But the second-order nonlinear susceptibility X-(2) of CND S/PMMA is improved compared with that of DANS/PMMA. The molecular second-or der polarizability beta of the CNDS/PMMA was estimated to be about 140 x 10 (-30) esu from the measured absorbance and X-(2) The relaxation of SHG inte nsity of CNDS/PMMA was slower than that of DANS/PMMA. This showed that CNDS is a kind of better dopant than DANS as second-order nonlinear-optical mat erial. (C) 1999 Elsevier Science B.V.