Some Approaches to Vacuum Uv and X-Ray Lasers

The ejection of electrons from inner shells of atoms through photoionization is suggested as a straightforward means of creating population inversions at vacuum uv and x-ray wavelengths. This can be accomplished by photon sources covering broad bands. Sodium vapor and solid copper are examined as possible candidates for laser action at 372 Å and 1.54 Å, respectively. A first-rise traveling wave pump must be used; pumping powers required for superradiant operation run into several gigawatts, with rise times ranging from 10−9 sec in the near-vacuum uv to 10−15 sec in the x-ray region.