Photoelectric, nonlinear optical, and photorefractive properties of polymer composites including carbon nanotubes and cyanine dyes

The effect of cyanine dye additives on the photoelectric, nonlinear optical, and photorefractive properties of polyvinyl carbazole composites based on closed single-walled carbon nanotubes has been investigated. It has been found that these characteristics are affected by the dye in which the lowest unoccupied molecular orbital (LUMO) lies below the level of the photoexcited nanotube. The addition of this dye to the composite leads to a 14-fold increase in the quantum efficiency of the generation of mobile charge carriers under irradiation by a laser (1064 nm) in the absorption region of the nanotubes. Moreover, the addition of the dye to the composite decreases the third-order susceptibility $\chi^{(3)}$, presumably, due to the opposite orientations of dipoles of the dye and the nanotube upon adsorption of the dye on the nanotube. The addition of the dye to the composite also provides a twofold increase in the two-beam photorefractive amplification factor of the laser beam with a wavelength of 1064 nm. The obtained values of the two-beam photorefractive amplification factor reach 120 cm$^{-1}$.