Absorption of Ultrashort Laser Pulses by Solid Targets Heated Rapidly to Temperatures 1–1000 eV

We report measurements of laser absorption for high-contrast ultrashort pulses on a variety of solid targets over an intensity range of 10¹³ to 10¹⁸ W/ cm². These data give an experimental determination of the target energy content and an indirect measure of dense plasma electrical conductivity. Our calculations accurately reproduce the behavior of aluminum targets, while the other materials show signs of additional absorption mechanisms. At high intensity all target materials reach a ``universal plasma mirror'' state and reflect about 90% of the incident light.