Photorefractive trapping and the correlation between recording and erasuredynamics in a polymer composite

The fast time constants of holographic contrast growth and erasure for vari ous photorefractive polymer composites were measured under a wide range of experimental conditions. Either of two sensitizers, 2, 4, 7-trinitro-9- flu orenone (TNF) or (2,4, 7-trinitro-9-fluorenylidene) malonodinitrile (TNFDM) , were used in a degenerate four-wave mixing experiment under varying condi tions of field, wavelength and intensity. Collected together, the fast grow th and erasure time constants were found to be correlated with a coefficien t of 0.96. From this correlation we conclude that the charge generation pro cess during holographic recording and the optical de-trapping process durin g hologram erasure are indistinguishable. Hence in accordance with the phot orefractive crystal model, hole recombination with the sensitizer anions fo rms the primary charge trapping mechanism in the majority of photorefractiv e polymer composites.