Advanced Functional Materials, Vol.18, No.2, 362-368, 2008
Photorefractive performance of hyperstructured cyclotriphosphazene molecular glasses containing carbazole moieties
Two hyperstructured photorefractive (PR) molecular glasses (M1 and M2) with a cyclotriphosphazene core are synthesized via nucleophilic substitution and an azo-coupling reaction. These molecules exhibit excellent solubility in common organic solvents and maintain a complete amorphous state in spite of their high glass-transition temperature. The nonlinear optical effects, two-beam coupling and four-wave mixing, respectively, are used to prove the PR performance in the optically transparent films of M1 and M2 doped with 30 % N-ethyl-carbazole. With no external electric field, a gain coefficient of 102 cm(-1) and diffraction efficiency of 24 % are obtained in the composite made from M1, and an even higher gain coefficient of 21-4 cm(-1) and diffraction efficiency of 31 % are obtained in the composite made from M2 owing to its higher chromophore loading.