Direct observation of density-gradient effects in harmonic generation from plasma mirrors
S. Kahaly, S. Monchocé, H. Vincenti, B. Dromey, M. Zepf, Ph. Martin, and F. Quéré
Accepted
High-order harmonics and attosecond pulses of light can be generated when ultraintense, ultrashort laser pulses reflect off a solid-density plasma with a sharp vacuum interface, i.e. a plasma mirror. We demonstrate experimentally the key influence of the steepness of the plasma-vacuum interface on the interaction, by measuring the spectral and spatial properties of harmonics generated on a plasma mirror whose initial density gradient scale length L is continuously varied. Time-resolved interferometry is used to separately measure this scale length.