Silver nanocolloid as optical bistable device under continue wave laser illuminations

In this study, Kerr effect nonlinearity of silver nanocolloids due to thermal effect is investigated experimentally. Silver nanoparticles are synthesized by chemical reduction method in stable colloidal form in water. The diameter of silver nanoparticles is about 20 nm. Experimental results concerning the optical bistability of the nano-colloid are performed under CW laser illuminations. Two different CW laser beams (He-Ne and Nd-Yag lasers) were used to interact with a vertical Fabry-Perot interferometer containing a cell of nanocolloid. Hysteretic loops are observed due to optical bistability. Furthermore, nonlinear refractive indexes versus incident intensities are evaluated using close aperture z-scan method. It gives more precise values of nonlinear refractive indices that help in numerical drawing of Hysteretic loops. Experiments showed silver nanoparticles have good potential for semi-fast optical switcher devices in both red and green wavelengths.