Stimulated low-frequency scattering of light in an aqueous suspension of the tobacco mosaic virus

Stimulated low-frequency scattering of light by aqueous suspensions of the tobacco mosaic virus with the scattering frequency depending on the concentration of the virus is observed for the first time. For concentrations of $\sim1 \times 10^{12}$ and $\sim 2 \times 10^{12}$ cm$^{-3}$, the Stokes components of scattered light are shifted by $\sim 43.99$ and $\sim 31.08$ GHz, respectively. At the same time, the competing process of stimulated Brillouin scattering in these heterogeneous media is suppressed. The theory of stimulated emission resulting from normal-mode vibrations of solvent-molecule-loaded cylindrical nanoparticles driven by ponderomotive forces in the field of two copropagating pump electromagnetic waves is developed for the first time. The theoretically estimated frequency shift of the Stokes component is $\sim 50$ GHz, which agrees with the experimental result. It remains unclear why a decrease in the thickness of the liquid layer with a simultaneous increase in concentration selectively favors a decrease in the frequency of coherent normal-mode vibrations of the virus participating in stimulated low-frequency scattering.