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

In a large-aperture KrF laser amplifier, steady-state gain is heavily reduc ed by intra-cavity amplified spontaneous emission (ASE). However, the reduc ed 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 t o explain the experimental results. However, a discrepancy was noticed betw een the experimental results and the calculated values, which was due to th e 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 cod e. The calculated values agreed with the experimental results.