Demonstration of saturated high repetition rate tabletop soft x-ray lasers at wavelengths down to 13.2 nm

We have demonstrated gain-saturated operation of high repetition rate table-top soft x-ray lasers producing microwatt average powers at wavelengths ranging from 13.2 to 32.6 nm in transitions of Ni-like and Ne-like ions. Lasing was also observed for shorter wavelength transitions of the 4d¹S ₀→4p¹P₁ Ni-like isoelectronic sequence, with amplification approaching gain saturation in the 11.9 nm line of Ni-like Sn and progressively reduced gain for wavelengths as low as 10.9 nm in Ni-like Te. The results were obtained heating a pre-created plasma with a picosecond optical laser pulse with an energy of only 1 J impinging at optimized grazing angles of incidence for maximum pump energy deposition efficiency. This pumping geometry takes advantage of the refraction of the pump beam to increase the energy deposition efficiency of the pump beam into the gain region, making it possible to operate soft x-ray lasers in this wavelength range at significantly increased repetition rates. The results demonstrate the feasibility of producing high average powers of coherent radiation in the 100 eV spectral region for applications using a table-top source.