Multiple Pulse Effects In Transient Stimulated Raman Amplification

ABSTRACT Transient stimulated Raman amplification of a pulse in a pulse train can be considerably greater than that of an isolated pulse if the pulses are sufficiently close together. We describe thecharacteristics of gain buildup in a pulse train theoretically and report experimental observations ofamplification increases of 4 orders of magnitude in 4 pulses. The effect of phase alternation of the Stokes seed on the gain buildup is also described. i.INTRODUCTION The transient stimulated Raman amplification of a pulse within a pulse train can be affectedby the presence of the other pulses. If the pulses are spaced sufficiently close together relative to thedephasing time, T2, the growth of a given pulse in the train is determined by the phonons left behindby the preceeding pulses as well as by the photons in the corresponding pump pulse. As a result theamplification of a particular pulse in the train can be higher by several orders of magnitude than thecorresponding gain of an isolated pulse. This behavior is illustrated schematically in Fig. 1.