Photoionization lasers pumped by broadband soft‐x‐ray radiation from laser‐produced plasmas

Large population inversions have been obtained in Cd and Zn ions using broadband soft‐x‐ray radiation from laser‐produced plasmas to photoionize and thereby remove inner‐shell d‐electrons from the neutral atoms. This technique has presently produced lasers in the ultraviolet, visible and near infrared. The use of optical pumping to transfer the population produced by photoionization to higher lying levels may produce VUV and XUV lasers in the same and other species. Gains as high as 40 cm−1 and inversion densities as high ad 1015 cm−3 have already been observed. These large inversions suggest that extractable energies approaching 1 mJ/cm3 may be possible for directly‐pumped lasers operating in the visible and for transfer‐pumped lasers operating at shorter wavelengths.