Saturated and Short Pulse Duration X‐Ray Lasers

The basis of a model of the relationship between gain and output laser intensity is reviewed and the measurement of the duration of X‐ray lasing with a streak camera with 700 fs temporal resolution is described. Combined with a temporal smearing due to the spectrometer employed, we have measured X‐ray laser pulse durations for Ni‐like silver at 13.9 nm and Ne‐like nickel at 23.1 nm with a total time resolution of 1.1 ps. An extension of the model is shown to consistently relate the measured X‐ray laser pulse duration to estimates of the gain duration obtained by temporally resolving resonance line emission from states near in energy to the upper lasing level.