EFFICIENT, HIGH-BRIGHTNESS SOFT-X-RAY LASER AT 21.2 NM

In this paper we review the development of a soft-x-ray laser at 21.2 nm, recently carried out at the Laboratoire de Spectroscopie Atomique et Ionique. Amplification is generated by electron collisional pumping on a 2s(2)2p(5)3p-2s(22)p(5)3s, J=0-1 transition in neonlike zinc (Zn 20+). The lasing medium is a similar to 150 mu mx2 cm line plasma prod uced by irradiating slab Zn targets at a net intensity of similar to 1 .4x10(13) W cm(-2) using a 1.06-mu m, 600-ps-long pulsed laser deliver ing similar to 350 J of net energy on the target. Accompanying the dri ving pulse by a 100-mJ-level prepulse train through deliberately imper fect isolation of the mode-locked laser oscillator, the J=0-1 gain coe fficient similar to 5 cm(-1) is generated. The emission appears in an similar to 100-ps burst and precedes the lasing on both the much weake r J=2-1 lines and the x-ray continuum peak. The J=0-1 output source re gion, the beam spatial profile, and its time historyhave been measured and their relevance to the kinetics of this lasing system is discusse d. A half cavity was implemented and a strong double-pass amplificatio n at 21.2 nm with a 2-cm-long plasma obtained. With the gain-length pr oduct achieving similar to 17.3 according to the particular configurat ion, saturation was demonstrated, which is confirmed through a schemat ic model of the level kinetics. To our knowledge, it is the first neon like soft-x-ray laser where saturation on the J=0-1 line was achieved by using a half-cavity arrangement. Absolute energy measurements indic ate similar to 400 mu J in the half-cavity-generated beam and a peak o utput power of similar to 5 MW, which makes this laser one of the most efficient soft-x-ray lasing systems demonstrated to date.