3A11 High-speed formation of diffraction gratings in azobenzene liquid crystal films by pico-second laser pulses

Abstract

Formation of diffraction gratings in polymer azobenzene liquid crystal films was investigated by pico-second laser pulses. On irradiation of interfered pulses at 355 nm (Nd : YAG ; 20 ps, fwhm), the first-order diffraction of a readout beam at 633 nm was immediately observed. It was found that the diffraction signal rose up in approximately 250 ns. With an increase in the light intensity, the diffraction efficiency also increased. From the diffraction efficiency, the modulation of refractive index (Δn) was evaluated. The value of Δn was estimated as 0.07 at the maximum diffraction efficiency. These results suggest that the diffraction gratings formed in the polymer films were based on the photochemical N-I phase transition of the azobenzene liquid crystal.