A time-dependent ASE calculation for transient gain enhancement. of picosecond pulses in a large-aperture KrF laser amplifier

Abstract.

In a large-aperture KrF laser amplifier, steady-state gain is heavily reduced by intra-cavity amplified spontaneous emission (ASE). However, the reduced gain can 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 and numerical calculations to explain the experimental results. However, a discrepancy was noticed between the experimental results and the calculated values, which was due to the neglect of the propagation time of laterally traveling ASE. In this paper, we present a novel time-dependent ASE code incorporating the lateral-ASE transit time and report the calculation results using the developed ASE code. The calculated values agreed with the experimental results.