Development of Composite Nonlinear Optical Materials Based on Local Field Enhancement

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9223726 Boyd We will perform experimental and theoretical work aimed at the development of new nonlinear optical materials with improved nonlinear response. The basic idea of our approach is to form a composite material of two (or more) constituents that differ both in their linear and nonlinear optical properties. The electric field of an applied optical wave will therefor be nonuniformly distributed between the two constituents, leading to an effective nonlinear susceptibility of the composite that can exceed that of either of its constituent materials. In our initial theoretical studies, we have discovered realistic conditions in which such a local-field enhancement can be at least a factor of five. In our approach, both constituents can be optically lossless, and thus our approach should be distinguished from recent work involving metal colloids and semiconductor-doped glasses in which the composite material is necessarily absorbing. Experiments to be performed as part of this investigation are aimed both at developing a fundamental understanding of the role of local field effects in determining the nonlinear optical properties of composite materials and at developing actual composite materials with improved nonlinear response. Our method is general in scope, that is, it is applicable to both second- and third-order nonlinear optical materials and it can be used to increase the nonlinear optical response of essentially any homogeneous optical material by forming a composite out of that material. However, our initial experimental studies will consider the enhancement in the nonlinear optical properties of polymeric optical materials. ***