High-energy conversion efficiency of transient stimulated Raman scattering in methane pumped by the fundamental of a femtosecond Ti:sapphire laser

We studied stimulated Raman scattering in pressurized methane in the highly transient regime pumped by 140-fs 0.7-mJ pulses from a Ti:sapphire (Ti:S) laser tuned at 750 nm. Energy-conversion efficiency of the first Stokes of more than 15% was achieved, with no strong sign of saturation with as much as 40 atm $\left(1 \mathrm{atm}=760 \mathrm{Torr}\right)$ of Raman gas pressure. To our knowledge, this is the highest conversion efficiency of transient stimulated Raman scattering generated directly from the fundamental of a Ti:S laser.