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 3d(1)S(0)-4p(1)P( 1) transition at 32.6 nm by a novel excitation scheme. In this scheme, Ni-l ike ions are prepared with almost 100% abundance by optical-field-induced i onization 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 (N-c = 5.6 x 10(19) cm(-3)) for a dr iving laser intensity of 1.75 x 10(16) W/cm(2). With longitudinal pumping, an output energy greater than 40 muJ and an energy efficiency of 7 x 10(-5) are expected with 200 Torr Kr gas.