Nonlinear Amplification of Light Pulses

The passage of a powerful light pulse through an optical quantum amplifier operating under saturation conditions is investigated theoretically and experimentally. It is shown that during nonlinear amplification the pulse peak moves with a velocity which considerably exceeds the velocity of light, the duration of the pulse remaining practically unchanged. In order to decrease the pulse duration during nonlinear amplification, the slope of the incoming pulse front should be increased. This is realized in the experiments by cutting off of the leading front with the aid of an additional shutter. The duration of the pulse with such a front was made as low as 4. 7 nsec during nonlinear amplification.