Accessing the optical nonlinearity of metals with metal-dielectric photonic bandgap structures

Metals typically have very large nonlinear susceptibilities (similar to 10( 6) times larger than those of typical dielectrics), but because they are ne arly opaque their nonlinear properties are effectively inaccessible. We dem onstrate numerically that a multilayer metal-dielectric structure in which the metal is the dominant nonlinear [chi((3))] material can have much large r intensity-dependent changes in the complex amplitude of the transmitted b eam than a bulk sample containing the same thickness of metal. For 80 nm of copper the magnitude of the nonlinear phase shift is predicted to be as mu ch as 40 times larger for the layered copper-silica sample, and the transmi ssion is also greatly increased. The effective nonlinear refractive-index c oefficient n(2) of this composite material can be as large as (3 + 6i) x 10 (-9) cm(2)/W, which is among the largest values for known, reasonably trans missive materials. (C) 1999 Optical Society of America OCIS codes: 190.0190 , 190.4400.