Gain scaling of short-wavelength plasma-recombination lasers

The theoretical Z(7.5) dependence of the small-signal gain of plasma-recombination lasers on the ionization stage Z of the laser species implies a straightforward development of short-wavelength lasers but appears to be significantly larger than the experimentally achieved gain scaling. A new analysis, which incorporates a simple experimental parameter representing the efficiency of populating the upper level at a given plasma electron density, results in a gain scaling with ionization state (Z(4.5)) that is more consistent with experiments and also reveals a need for better experimental control of the ion-production and electron-ion-recombination processes when one attempts to make such lasers.