Effects of Saturable Absorber Lifetime on the Performance of Giant-Pulse Lasers

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Abstract
An earlier paper on the theory of saturable absorber giant‐pulse lasers is extended by considering the effects of a finite absorber lifetime ts on the pulse parameters. Digital‐computer studies show that for typical systems the giant‐pulse energy and peak power are practically unchanged from the case for which ts → ∞. A new result is that the initial cavity photon density or, alternately, the pump power, must exceed a threshold value to proceed from the region of initial normal lasing to giant pulsing. The role of the pump in the pulse buildup from noise is examined, in particular the transition region between the low‐level behavior described by Sooy and the onset of absorber saturation. The ratio of photon density in the transition region to the peak density is shown to provide a measure of the product of the ratio of absorber‐to‐laser cross section times the absorber lifetime. Some possible mechanisms which lead either to mode selection or mode locking in passive Q‐switched lasers are discussed.