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Theory of Second Harmonic Generation in Composites of Nonlinear
Dielectrics

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P. M. Hui, Department of Physics, The Chinese University of Hong Kong,
Shatin, New Territories, Hong Kong,
and D. Stroud,
Department of Physics, The Ohio State University,
Columbus, Ohio 43210-1106

We consider the effective nonlinear susceptibility tensor
d(-2\omega; \omega, \omega) for second harmonic
generation in a nonlinear composite medium. We derive a simple expression
for this susceptibility in terms of the position-dependent tensor d,
and three factors which describe the local field
enhancement in a corresponding linear medium. The resulting expression
can be used to calculate the local-field enhancement of d in many
geometries. In the dilute limit, the general expression reduces
to a result previously derived.
PACS Nos. 42.70.Nq, 42.65.Pc, 78.66.Sq