Induced Dopant-Assisted Molecular Reorientation and Trans-Cis Isomerism

LASER-INDUCED DOPANT-ASSISTED MOLECULAR REORIENTATION AND TRANS-CIS ISOMERISM 

In nematic liquid crystals doped with some absorbing dye molecules, studies have shown that the excited dye molecules could exert an intermolecular torque Tmoi on the liquid crystal molecules that could be stronger than the optical torque Top. In particular, Janossy et al. have observed that some classes of anthraquinone dye molecules, when photoexcited, will exert a molecular torque Xmoi l op, with ri that 

An interesting and important point is that, at low optical power, the orientational effect actually is the dominating one, even in such highly absorptive material. In other recent studies of dye-doped nematic liquid crystals, observed nonlinearities have approached the so-called supranonlinear scale characterized by refractive index coefficients n2 1 cm /W. The observed nonlinearity is orders of magnitude larger than the so-called giant optical nonlinearity of pure liquid crystals. In particular, methyl-red dye-doped nematic liquid crystals were first observed to have a nonlinear index 

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