SYNTHESIS AND CHARACTERIZATION OF HIGHLY EFFICIENT PHOTOREFRACTIVE POLYMER COMPOSITES WITH LONG PHASE-STABILITY

We have synthesized the chromophores 4-[(4'-nitrophenyl)azo]-1,3-bis[( 3 ''- or 4 ''-vinylbenzyl)oxy]benzene (NPADVBB) and 4-[(4'-nitrophenyl )azo]-1,3-bis(benzyloxy)benzene (NPADB). New polymer composites based on the photoconductor poly(9-vinylcarbazole), the plasticizer 9-ethylc arbazole, NPADVBB, and the sensitizers 2,4,7-trinitro-9-fluorenone and (2,4,7-trinitro-9-fluorenylidene)malonitrile were prepared. Ellipsome tric measurements and degenerate four-wave mixing experiments were per formed at 633 and 830 nm. The composites showed excellent phase stabil ity, and nearly complete diffraction was observed at 633 nm. The two-b eam coupling gain was limited by the small phase shift between the int erference pattern and the index grating.