The experimental study of the amplification of stimulated Raman scattering (SRS) in high purity H2 gas was demonstrated employing a Q-switched Nd:YAG laser at 1064 nm as the pump source. A part of the 1064 nm pump light (20% in energy) was focused into the first H2 gas cell to generate the backward first Raman Stokes light (BS1), which is taken as the Raman seed light. The BS1 seed light combined to the residual pump light were focused into the second H2 gas cell to get the amplification of the S1 1900 nm infrared Raman light. In this study, the maximum quantum conversion efficiency of the S1 light was estimated to be 76%. Under the condition of the same pump energy, especially for the low pump energy (lower than 40 mJ), the quantum conversion efficiency of the S1 light with the Raman seed light was significantly increased comparing to the single focus geometry (without the Raman seed light).
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