Control of the intensity of a single harmonic generated in laser plasma by varying the chirp of intense femtosecond pulses

A significant increase, as well as a decrease, in the intensity of single higher harmonics of femtosecond radiation of a Ti:sapphire laser that are generated in a weakly excited laser plasma on the surface of GaAs, Cr, InSb, In, and stainless steel is demonstrated. The intensities of some higher harmonics in different regions of their plateaulike distribution varied from a 23-fold excess over the intensity of the neighboring harmonics to the complete absence in the extreme ultraviolet spectrum. The specific features of a 200-fold increase in the intensity of the 13th harmonic generated in indium plasma are analyzed. These variations in the intensity distribution of harmonics in the plateau region are obtained by varying the chirp of laser pulses.