High Optical Non linearity of Nematic Liquid Crystals Doped with Gold Nanoparticles

Tetraoctylammonium bromide (TOAB)-coated gold nanoparticles dispersed in nematic liquid crystals lead to an enhancement of the nonlinear index coefficient, n(2). A small amount of particles is sufficient to increase n2 and two-beam coupling gain by more than an order of magnitude while maintaining high optical quality and the ability of the suspensions to withstand strong applied electric fields. However, TOAB plays a crucial role in increasing the pretilt angle and reducing the anchoring strength, which leads to a stronger modulation of both the reorientation and the refractive index of liquid crystal suspensions.