Design of an Ultrahigh-Gain Ni-like Kr Soft-X-Ray Laser by Use of an Optical-Field-Induced Ionization-Initiated Transient Collisional Excitation Scheme

We propose a Ni-like Kr soft X-ray laser operating on the 4d1S0–4p1P1 transition at 32.6 nm by a novel excitation scheme. In this scheme, Ni-like ions are prepared with almost 100% abundance by optical-field-induced ionization and the inverse bremsstrahlung heats the plasma efficiently. The numerical simulation predicts that an ultrahigh gain greater than 1000 cm-1 is achievable in low-density plasma (Ne=5.6×1019 cm-3) for a driving laser intensity of 1.75×1016 W/cm2. With longitudinal pumping, an output energy greater than 40 µJ and an energy efficiency of 7×10-5 are expected with 200 Torr Kr gas.