Gold nanoparticle liquid crystal composites as a tunable nonlinear medium.

We investigate the nonlinearity of a liquid crystal cell doped with gold nanoparticles by considering their selective absorption. Such nonlinearities are promising for optical processing applications and optical limiters. Systems displaying thermal nonlinearities are particularly attractive as the maximum nonlinearity may occur in the absence of an applied field and additionally this nonlinearity can be controlled by the reorientation of the liquid crystal. We show that there exists a theoretical optimum concentration of absorbers, which maximizes the nonlinearity. Further we show that the nonlinearity of the system can be tuned by the reorientation of the liquid crystal host, with the nonlinearity decreasing from 9 × 10(-5) cm(2)W(-1) to zero by the application of a magnetic field of the order of 0.01 Tesla. This allows a fine control of the diffraction efficiency and, in principle, many other nonlinear effects.