Dispersion of third-order nonlinear optical susceptibility of silver nanocrystal-glass composites

We have investigated dispersion of third-order nonlinear optical susceptibility, chi((3)), for a silver nanocrystal-glass composite around the surface plasmon resonance band. A real and an imaginary part of chi((3)) have been separately measured by a Z-scan method. The maximum value of imaginary chi((3)) is - 1.5 x 10(-10) esu at 2.97 eV and the real chi((3)) value ranges from -4.4 x 10(-11) to + 4.4 x 10(-11) esu. We have calculated dispersion curves of the composite assuming that the real and imaginary parts of dielectric constant of metal nanocrystals are changed due to the creation of hot electrons by optical excitation. The dispersion curves near the surface plasmon band show features characteristic of the composite system, which is not described by a two-level atomic model. (C) 2000 Elsevier Science B.V. All rights reserved.