Compression of light pulses by stimulated Raman scattering without a frequency shift

A system for compressing light pulses without altering the frequency of the original laser radiation is proposed and implemented. Such a system allows further amplification of laser radiation. The conversion in the system occurs in two stages: stimulated Raman scattering conversion of a pulse under counterpropagating amplification conditions and conversion of a compressed Stokes pulse into anti-Stokes radiation of frequency equal to the initial pump frequency. A report is given of the use of stimulated Raman scattering in compressed methane in such a system to shorten pulses of the second harmonic of an Nd laser (λ = 0.528 μm) from 3 ns to 100 ps.