Light-wave mixing and scattering in quantum gases
L. Deng, Chengjie Zhu, and E. W. Hagley
Accepted
We present a semi-classical theoretical framework on light-wave mixing and scattering in single-component quantum gases. We show that these optical processes originating from elementary excitations with dominant collective atomic recoil motion are {\it stimulated} Raman or hyper-Raman in nature. In the forward direction, the wave-mixing process, which is the most efficient process in normal gas, is strongly reduced by the condensate structure factor even though the Bogoliubov dispersion relation perfectly compensates the optical-wave phase mismatch. In the backward direction, however, the free-particle-like condensate structure factor and Bogoliubov dispersion result in highly efficient light-wave mixing and collective atomic recoil motion that are enhanced by a {\it stimulated} hyper-Raman gain and a very narrow two-photon motional state resonance.