REDUCED FRACTIONAL ABSORPTION AND 2ND-HARMONIC EMISSION IN LASER-PRODUCED PLASMAS

Both particle-in-cell and Vlasov simulations of the collective absorpt ion of p-polarized intense laser light incident on a plasma with a ste ep density profile show the fractional absorption decreasing with inte nsity for large angles of incidence. Here an analytical model is devel oped that indicates that this effect for a high-temperature plasma (T- e greater than or equal to 2.5 keV) is connected with the conversion o f a large fraction of the incident energy into harmonic emission. Good agreement between the results of Vlasov simulations and those of the nonlinear analytical model are obtained. (C) 1997 American Institute o f Physics.