Efficient stimulated-Raman-scattering converter for subnanosecond light pulses

An experimental study was made of the characteristics of time-dependent stimulated Raman scattering in methane. The first-Stokes-component pulse formed from spontaneous noise was found to be displaced relative to the unconverted part of the pump pulse by 0.4 of the duration of the latter, in the range 0.1–1 nsec. Taking this into account, a "series" stimulated-Raman-scattering amplifier was designed with a 70% efficiency and a Stokes radiation output power of 500 MW with a divergence of less than ~3x10^–4 rad. The possibility of employing a multipass "series" Raman amplifier for effective compression of light pulses in time is discussed.