Observation of super Coster-Kronig-pumped gain in Zn iii

Abstract

We report the observation of laser gain in the vacuum ultraviolet pumped by super Coster-Kronig decay. Using a 5-J, 300-psec pump pulse of 1064-nm radiation, we have observed gain on transitions in Zn II at 127.0, 130.6, and 131.9 nm with total gains of exp(2.4), exp(5.1), and exp(3.2), respectively. The large branching ratios of the rapid super Coster-Kronig decay into a small number of final levels makes high-efficiency operation possible.The use of selective Auger decay to produce population inversion and gain in the soft-x-ray and ultraviolet spectral regions was proposed by McGuire' in 1975. The first successful experiments were performed by Kapteyn et al. 2 in 1986; in those experiments 55 J of 1064-nm pump energy was used to produce incoherent soft x rays, which photoionized Xe I. These atoms Auger decayed to Xe III to produce a gain of exp (7) at 109 nm. Experiments by Yin et al. 3 showed that comparable gains on this transition could be obtained with less than 1 J of pumping energy. Recently Sher et al. 4 used a traveling-wave geometry to obtain a small-signal gain of exp (40) and a saturated output energy of 20 LJ at 109 nm.In this Letter we follow the proposal of Mendelsohn and Harris 5 to obtain gain by selective super CosterKronig decay of photoionization-pumped Zn I. A super Coster-Kronig decay process is a subclass of an Auger process in which the initial hole, the jumping electron, and the departing electron all occupy the same n shell. As a result, the decay rate is very fast (typically >1015 sec-'), and therefore the process dominates other Auger processes. In particular, the branching ratio to the upper level for the Zn system described here is 27%, while that to the lower laser level is <1%. For the 109-nm Xe system, the Auger decay rates to the upper and lower laser levels are about equal, 6 and an inversion results from the higher degeneracy of the lower level. We have observed gain on transitions in Zn III at 127.0, 130.6, and 131.9 nm with total gains of exp(2.4), exp(5.1), and exp(3.2), respectively.The relevant energy levels of the Zn system are shown in Fig. 1

Development and Application of XUV Lasers

“…We report a significant advance toward this goal: the first xuv laser system pumped by a standard, commercially available, Nd:YAG laser system at high repetition rate. Gain in the XUV has been observed in several atomic species, including C[1], Cs [2,3], Zn [4], Kr, and Xe [5,6]. We chose to develop the Xe+ 2 Auger laser at 109 nm because of its unique combination of high gain, efficiency, benign physical properties, and short wavelength.…”