Anomalous Transmission through Thin Al Foils Driven by High Contrast Ultra-intense Laser*

The light transmittance of 0.01{\%} through 0.8 $\mu $m thick Al foils at a wavelength of 527 nm was measured by illuminating frequency doubled 400fs duration laser pulses at an intensity of 2x10$^{19}$ W/cm$^{2}$. Relativistic electrons generated in the interaction could emit radiation due to the ``transition radiation'' or newly considered process ``Larmor radiation in sheath field.'' These two processes are compared with experimental results from T$^{3}$ laser system and kinetic simulations of laser pulse interaction with a foil using adaptive PIC-Vlasov hybrid code.