Reversible and irreversible index gratings in a NPP-doped low-T-g polymer composite

A reversible photorefractive grating and an irreversible local photo-induce d aggregation grating were observed in a low glass transition temperature p olymer composite poly( N-vinylcarbazole): 2,4, 7-trinitro-9-fluroenone: N-e thylcarbazol: N-(4-nitrophenyl)-(1)-prolinol. Two gratings were distinguish ed by using the two-beam coupling (TBC) experiment and the four-wave mixing experiment. For photorefractive grating, the TBC coefficient was measured to be 140 cm (1) at an applied electric field of E-0 = 85V/mum, correspondi ng to a photorefractive grating of 3.6 x 10(3). The photo-induced aggregati on grating was measured to be about 7 x 10(3).