ABSTRACT
Lasing in the extreme ultraviolet and soft X-ray regions has been achieved in highly ionized plasmas, generally produced by pulses from highpower lasers incident on solid targets. Free electron lasers are divided into short and long wavelengths because different physical processes are involved. Nuclear pumped lasers have been demonstrated to operate pulsed or steady-state over a wavelength range extending from the vacuum ultraviolet to the infrared using a variety of gases and molecules. Excitation resulting in a core level hole creates an inverted electron population with respect to the filled valence band and hence laser action is possible. Nuclear pumped lasers have been demonstrated to operate pulsed or steady-state over a wavelength range extending from the vacuum ultraviolet to the infrared using a variety of gases and molecules. The lasers have been operated in a continuous wave mode; the amplifier experiments have measured transient gain or gain on a probe laser pulse.
