Generation of high average power and Millijoule-level pulses with a table-top soft x-ray laser

Millijoule-level laser pulses and multi-milliwatt average power have been obtained for the first time from a table-top soft x-ray laser. Laser pulses with energy up to 1 mJ and an average power of approximate to 3.5mW were generated at a wavelength of 46.9 nm by single pass amplification in a 34.5 cm long Ne-like Ar capillary discharge plasma. The large gain-length product of this plasma column allows for soft x-ray amplification in a highly saturated regime, resulting in very efficient energy extraction. An average laser output pulse energy of 0.88 mJ and peak power of 0.6 MW were obtained at a repetition rate of 4 Hz. The spatially coherent average power emitted by this 26.5eV laser is comparable to that generated at this photon energy in a similar bandwidth (Delta lambda/lambda = 10(-4)) by a third-generation synchrotron beam-line, while its peak spatially coherent power exceeds that of the undulator by several orders of magnitude. With an estimated peak spectral brightness of approximate to 1x10(23) photons/(s mm(2) mrad(2) 0.01 % bandwidth) this table-top laser is one of the brightest soft x-ray sources to date.