Saturation behavior of two x-ray lasing transitions in Ni-like Dy

Saturated operation of a laser at a wavelength shorter than 6 nm is demonst rated. The output of the Ni-like Dy laser at 5.86 and 6.37 nm, pumped by th e VULCAN 1.05-mu m Nd-glass laser in a 75-ps double-pulse configuration at 2 x 10(13) W cm(-2) peak irradiance, is measured experimentally and studied theoretically using a rate equation and one-dimensional amplified spontane ous-emission model. The experimental results and modeling show that, upon s aturation, the output intensities from the lower gain lasing transition at 6.37 nm decrease with increasing gain medium length. This is a different si gnature of gain saturation for Ni-like lasers and is desirable for applicat ions, as it shows that one lasing transition will dominate with Ni-like las ers in saturation. [S1050-2947(99)50901-3].