Calculation of transient gain enhancement by suppressing intra-cavity ASE in a large-aperture KrF laser amplifier

In a large-aperture amplifier, steady-state gain is heavily reduced by the intra-cavity amplified spontaneous emission (ASE). However, the reduced gain could be transiently enhanced by temporally suppressing the ASE with an intense depleting short pulse. Previously, we reported the experimental observation of this transient gain enhancement in a KrF laser amplifier with a 29-cm-diameter aperture. In this paper, this transient gain enhancement is examined theoretically by using a time-dependent ASE code. From a comparison of the code calculations with the experimental results, the observed quick gain recovery and also the possibility of a transient gain higher than the steady-state value are discussed. Received: 18 February 1999 / Revised version: 5 March 1999 / Published online: 28 April 1999