Reversible and irreversible index gratings in a NPP-doped low-T<SUB>g</SUB> polymer composite

Abstract

A reversible photorefractive grating and an irreversible local photo-induced aggregation grating were observed in a low glass transition temperature polymer composite poly(N-vinylcarbazole): 2,4,7-trinitro-9-uroenone: N-ethylcarbazol: N-(4-nitrophenyl)-(l)-prolinol. Two gratings were distinguished by using the two-beam coupling (TBC) experiment and the four-wave mixing experiment. For photorefractive grating, the TBC coeae cient was measured to be 140 cm -1 at an applied electric eld of E 0ˆ8 5V=·m, corresponding to a photorefractive grating of 3:6 £ 10 ¡3 . The photo-induced aggregation grating was measured to be about 7 £ 10 ¡3 :Journal of Modern Optics