The development of a pump laser for x-ray lasers that operate at wavelengths longer than 1 (mu) would permit the attainment of higher electron temperatures for a given pump intensity. Such a system would be of interest for electron collisional schemes at low Z, and would have the potential to improve the overall system efficiency. An initial design for an optical parametric oscillator that would down-convert 1 (mu) radiation to 2 (mu) is presented.
Peter L. Hagelstein,
"Transient x-ray laser schemes at 1 um and at 2 um", Proc. SPIE 1551, Ultrashort Wavelength Lasers, (5 February 1992); doi: 10.1117/12.134827; https://doi.org/10.1117/12.134827