Laser-driven parametric amplification of soft X-rays

Here we present the first experimental realization of a new x-ray laser schema based on parametric amplification of high-order harmonic radiation. High order harmonic radiation can be enhanced by several orders of magnitude in a neutral noble gas pumped by intense laser pulses. With a simple model we can identify the necessary experimental conditions, the spectral range, and the magnitude of the gain. Amplification is experimentally demonstrated for two completely different sets of parameters. To realize parametric x-ray amplification around 50 eV, we used the femtosecond front-end of the PHELIX laser system delivering 350-fs long pulses with an energy of 10 m J at the wavelength of 1054 nm and a repetition rate of 10 Hz. For parametric amplification at around 300eV, we used a two-stage Ti: sapphire based amplifier running at 1 kHz. The output pulses were compressed in a filament to 6-fs with a final energy of 1.5 mJ.