Influence of ponderomotive force on interaction of ultrashort pulse laser with solid plasma

The influence of the ponderomotive force on interaction of the ultrashort pulse laser with the solid plasma was studied by measuring the frequency shift induced by the movement of plasma critical surface. When laser intensity reache 1017W/cm2, the ponderomotive force reduced the thermal expanding velocity of laserinduced plasma, and produced a very steep density profile. In this case, the vacuum heating becomes the dominant absorption mechanism instead of the resonant absorption.