Strongly coupled plasmas in femtosecond-laser heated solids

Summary form only given, as follows. Solids heated by femtosecond lasers at moderate irradiances (up to 10/sup 15/ W/cm/sup 2/) yield readily plasmas with near-solid densities and relatively low temperatures. Such strongly coupled plasmas have been the focus of many experimental investigations, the objective of which is to determine the plasma transport properties. In particular, the reflectivity measurement of Milchberg et al. (1988) suggested strong disagreements between observations and existing electrical conductivity models. This has stimulated further experimental and theoretical studies. More recently, a possible means of probing the plasma thermal conductivity via Doppler shift measurements on the reflected light from a heat front was reported (Vu et al., 1994). Using numerical simulations which treat self-consistently laser absorption and plasma hydrodynamics, we have examined the absorption of femtosecond laser light and the formation and propagation of a laser-driven heat front in a solid. In this paper, we will review two important findings: (i) the reconciliation between the earlier reflectivity measurements and plasma electrical conductivity models (Ng et al., 1994), and (ii) heat front propagation as a probe of both electrical and thermal conductivities.