Energy transfer between laser beams propagating through an atomic vapor

We show that it is possible to transfer energy efficiently between two laser beams of comparable intensity by means of the near-resonant nonlinear response of an atomic vapor. The coupling is due to stimulated Rayleigh scattering and occurs when the frequency difference between the two beams is approximately the inverse of lifetime of the excited atomic state. We have measured the coupling between two beams from an Alexandrite laser tuned near the $4^2$ $S_{1/2}$→$4^2$ $P_{3/2}$ potassium transition and found that one of the transmitted beams can contain up to 85% of the total incident energy.