  With 780-nm, 250-fs laser pulses, ultrafast optical nonlinearity has been
observed in a series of thin films containing 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% weight
percentage of titanium isopropoxide. TEM shows the presence of the
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.
