The threshold reduction of SRS in deuterium by multi-pass configuration

•The S1 threshold of D2 SRS pumped by 1064 nm is a magnitude lower than previous reported value.•The S1 photon conversion efficiency reached (56.1±4.4)%, it is the maximum conversion efficiency under the same condition.•The S2 threshold of D2 SRS pumped by 1064 nm is 10.9 mJ (2.2 MW).•The S2 photon conversion efficiency reached (32.9±3.8)%.

Stimulated Raman scattering (SRS) in compressed D2 gas pumped with nanosecond laser radiation at 1064 nm in a multi-pass configuration has been studied. The influence of D2 pressure and pass number on Raman thresholds and the conversion efficiencies for the first Stokes (S1) and second Stokes (S2) components has been investigated. It is shown that multi-pass configuration is very efficient for the substantial reducing of SRS thresholds for both S1 and S2 components and increasing their conversion efficiencies. In our work, the S1 threshold is approximately one order of magnitude lower than that reported in previous studies; the S1 conversion efficiency reached (56.1±4.4)% at pump energy of 33 mJ. The lowest S2 threshold in the experiment is 15 mJ (with a peak power of 3 MW), and the S2 conversion efficiency reaches (32.9±3.8)%.