Off-resonant nonlinear optical refraction properties of azo dye doped nematic liquid crystals

Nonlinear optical refraction properties of azo dye doped nematic liquid crystals were investigated with a He-Ne laser (lambda = 632.8 nm) as offresonant light irradiation using spatial self-phase modulation method. Compared with the experimental results of resonant light (lambda = 532 nm), the sample irradiated by He-Ne laser exhibited lower optical threshold and the number of diffraction rings was sensitive to the laser polarization. The mechanism of nonlinear optical response of azo dye doped nematic liquid crystals at 632.8 nm could be mainly attributed to photoisomerization effect. Moreover, the diffractions of holographic gratings recorded by He-Ne laser in azo dye doped liquid crystals were consistent with the grating formation based on photoisomerization effect. (C) 2016 Optical Society of America