Absorption of Ultrashort Laser Pulses in Strongly Overdense Targets
  We report on the first absorption experiments of sub-10 fs high-contrast Ti:Sa laser pulses incident on solid targets. The very good contrast of the laser pulse assures the formation of a very small pre-plasma and the pulse interacts with the matter close to solid density. Experimental results indicate that p-polarized laser pulses are absorbed up to 80 percent at 80 degrees incidence angle. The simulation results of PSC PIC code clearly confirm the observations and show that the collisionless absorption works efficiently in steep density profiles. 
M. Cerchez, R. Jung, J. Osterholz, T. Toncian, O. Willi, P. Mulser and   H. Ruhl