Abstract

The fundamental electronic properties of metals, such as the electrical conductivity and optical reflectivity, exemplify the coherent response of a free electron gas to an external electro-magnetic perturbation. Though these mundane manifestations of coherence have been in practical use long before the invention of lasers, there have been only a few direct investigations of this coherent response by the ultrafast spectroscopic techniques [1,2]. This is in part due to a perception the e-h pair phase and energy relaxation in metals is nearly instantaneous, and large (several, eV) inhomogeneous broadening of metallic bands, which can obscure the measurements of well-defined excitations.

© 2000 IEEE