PHOTOREFRACTIVE EFFECTS OBSERVED IN THE ORGANIC-CRYSTAL 2-CYCLOOCTYLAMINO-5-NITROPYRIDINE DOPED WITH 7,7,8,8-TETRACYANOQUINODIMETHANE

For the first time photorefractive effects have been observed in 2-cyclooctylamino-5-nitropyridine (COANP) single crystals doped with 7,7,8,8-tetracyanoquinodimethane (TCNQ). Light induced refractive gratings with diffraction efficiencies up to 0.1% have been measured. The results of holographic and beam coupling experiments for different light polarizations indicate that the effect is based on a light induced charge separation and a refractive index change due to the electron-optic effect of the resulting space-charge field. It is demonstrated that photoabsorption or photo chemical refractive index changes can be excluded as mechanisms for the observed effects. © 1990.