OPTICAL-FIELD-IONIZED PLASMA X-RAY LASERS

A tabletop x-ray laser scheme involving lasing to the ground state of an ion following optical-field-induced ionization by a high-intensity short-pulse laser is studied, The role of the ground state in reducing the saturation intensity is calculated to be larger for H-like ions as compared with the effect in Li-like ions. Energy efficiencies of order 10(-5) are calculated for the 3d5/2-2p3/2 transition at 98 angstrom in Li-like Ne. The efficiency calculations are based on a driving laser with an intensity of 3 X 10(17) W/cm2, a wavelength of 0.25-mu-m, a pulse duration of 100 fsec, and an input energy of 25-100 mJ. A correction to the standard stimulated Raman scattering growth rate is given for a finite laser pulse. Use of short pulses is shown to be sufficient to control heating from stimulated Raman scattering in Li-like Ne. Extending the scheme to shorter wavelengths (e.g., Li-like Al at 52 angstrom) is difficult because of reduced efficiencies and excessive electron heating from Raman scattering.