Ultrafast optical nonlinearity in poly(methylmethacrylate)-TiO2 nanocomposites

With 780-nm, 250-fs laser pulses, ultrafast optical nonlinearity has been observed in a series of thin films containing poly(methyl methacrylate) (PMMA)-TiO2 nanocomposites, which are synthesized by a simple technique of in-situ sol-gel/polymerization. The best figures of merit are found in one of the films prepared with a 60 wt % of titanium isopropoxide. Transmission electron microscopy shows the presence of 5-nm-diameter particles in the film. The observed optical nonlinearity has a recovery time of ∼1.5 ps. These findings suggest the strong potential of PMMA-TiO2 nanocomposites for all-optical switching.