Ultrahigh-gain Ni-like Kr soft X-ray laser by optical-field-induced-ionization initiated transient excitation scheme

摘要

We propose a novel transient collisional excitation scheme for Ni-like Kr (4d~1S_0-4p~1P_1) soft-x-ray laser at 32.8 nm. In this scheme, Kr atoms in a differentially pumped cell are longitudinally pumped by a picosecond Nd:glass laser pulse with a focal intensity of 2 x 10~(16) W/cm~2. Almost 100% of the Ni-like Kr ions are produced by optical-field-ionization, and the ps-pulse efficiently heats the Kr plasma by inverse bremsstrahlung. Numerical calculations predict that an ultrahigh-gain of greater than 1200 cm~(-1) is possible for the Ni-like Kr transition at 32.8 nm. Preliminary experimental results are also reported.