Composite material films: optical properties and applications.

The optical properties of the composite systems Ag-SiO(2), Si-SiC, and Ge-Al(2)O(3) are compared with the predictions of the Maxwell-Garnett and the effective medium theories. Only the Maxwell-Garnett theory predicts the characteristic optical features of granular metals-a red shift relative to the pure metal in the plasma resonance and a dielectric anomaly. In the case of Si-SiC, the observed red shift in the transverse optical phonon frequency is too small to allow one to discriminate between the two theories. In the case of the Ge-AI(2)O(3) films, both theories are in good agreement with the experimental results for the optical constants near the absorption edge. The use of composite films for photothermal conversion and other optical applications is discussed.