Is there a high frequency limit to laser action

A review and discussion of modern theories and results leads to the conclusion that an absolute upper bound exists to the photon energies for which laser action can occur, and that depending on the laser medium, it lies in the range between 1 and 100 MeV. At higher energies, a wave cannot grow as rapidly as it is depleted. The same restriction applies to frequency conversion devices employing nonlinear interactions.