PHOTON-INDUCED LOCALIZATION AND FINAL-STATE CORRELATION-EFFECTS IN OPTICALLY ABSORBING MATERIALS

Two consequences of the absorption of light in optically absorbing mat erials that appear not to have been recognized previously are: (1) loc alization of the final electron and hole states involved in the absorp tion process into wave packets and (2) propagation of these wave packe ts with their respective group velocities. We demonstrate the existenc e of these phenomena by applying first-order time-dependent perturbati on theory to a simple model that can be solved analytically even when correlations that are ordinarily discarded in the random phase approxi mation are retained. This approach provides a natural explanation of c omponents in surface- and interface-optical spectra that are related t o energy derivatives of the bulk dielectric function epsilon(b) and ap parent differences in nominally bulk critical point energies E-g and b roadening parameters Gamma depending on surface conditions. (C) 1998 A merican Vacuum Society.