Spectral composition of the harmonic radiation and its sensitivity to the seed-laser power in the zero-gain harmonic generation scheme

We consider the spectral composition of X-ray radiation produced in the zero-gain harmonic generation scheme, as well as its sensitivity to the fluctuations of the seed-laser power. Ultrahigh harmonics (up to 50-60) of the seed wave from an external sub-piccosecond terawatt laser are shown to be generated with a reasonable intensity. A small number of side-bands are shown to be present simultaneously with the central line. The central line intensity appears to be tolerant to the laser power fluctuations up to 10-15%.