Growth from spontaneous emission in a Raman multipass cell

Previous investigations of stimulated Raman scattering in a multipass cell have considered the amplification of a Stokes input pulse. They found that a simple plane-wave transient theory, appropriately scaled to include the multiple passes and focusing, matched experimental data well. In this paper, we investigate growth from spontaneous emission in a H₂ Raman multipass cell. We find that a fully-quantum-mechanical scaled plane-wave theory describes the growth from spontaneous emission well in the high-gain limit. However, in the low-gain regime there is a significant increase in the Stokes output which is not predicted by the scaled plane-wave theory.