Raman amplification of ultrashort laser pulses in microcapillary plasmas

Experimental evidences of Raman amplification of ultrashort pulses in microcapillary plasmas are presented. The amplification of 100–500 fs pulses was investigated in microcapillaries with different lengths. The experimental data, together with simulation results, indicate that the resonance condition for Raman amplification in high-density plasma, [formula presented] existed only in a very short plasma column. Such an assumption makes it possible to reconcile the experimental results and theoretical predictions. Investigations in very short microcapillaries (0.2–0.5 mm) with a broadband seed pulse further support this hypothesis and the amplification factor is in agreement with the linear growth rate.