Abstract

The use of optical-field ionization (OFI) allows to control both an ionic state and electron energy distribution, which is of importance for production of x-ray lasers[1-3]. We previously reported the observation of gain on the 13.5-nm Lyman-α transition of H-like Li ions by OFI of a preformed Li⁺ plasma [4]. The measured electron temperature of less than 1.5 eV was significantly lower than what is expected by an above-threshold ionization model [5,6]. However, wavelength scaling of this scheme is not clear because the required pump laser intensity rapidly increases with decrease of x-ray laser wavelengths. The increase of the pump laser intensity additionally causes harmful heating of the plasma by nonlinear interactions. The increase of the pump laser intensity which results in the requirement of a huge pump device also makes it quite difficult to realize a tabletop x-ray laser operating below 10 nm.

© 1997 Optical Society of America