Photorefractivity and transmission-type holograms of a poly(N-vinylcarbazole)-based composite with N-4-nitrophenyl-(l)-prolinol as chromophore

The photorefractivity of a poly(N-vinylcarbazole)/2,4,7-trinitro-9-fluorenone/N-4-nitrophenyl-(l)-prolinol/ N-ethylcarbazole composite was investigated by two-beam coupling and degenerate four-wave mixing experiments. The composite in a weight ratio 35 : 1 : 50 : 15 exhibited a 22% steady-state diffraction efficiency and 70 cm^-1 two-beam coupling coefficient at the applied external field of 55 V/μm. Zero applied field transmission-type holograms were observed in the photorefractive sample as well as the spin-coated thin film. The dynamic decay of diffraction light indicated that there existed two contributors with different phase-shift, and the slow decay time can be as long as several h under continuous illumination by the readout beam.