Effect of coupling strength on atomic-to-molecular condensate conversion in Raman photoassociation

Abstract

We study two-photon Raman photoassociation for creating a coherent molecular Bose-Einstein condensate (BEC) from an atomic BEC. By exploring the dynamics of the coupled system, we show that the atom-to-molecule conversion efficiency can be controlled by changing the atom-molecule coupling strength and the effective two-photon Raman detuning. Atom-molecule coupling strength and the effective two-photon Raman detuning can be controlled by changing the laser intensity. We analyze the dynamics of the coupled atom-molecular condensate system by changing the laser intensity over a broad range, keeping the effective two-photon Raman detuning fixed. The effective two-photon Raman detuning depends on the two-photon detuning, Rabi frequencies, and the light shifting (AC Stark shift) of the levels. To keep the effective two-photon Raman detuning fixed, the two-photon detuning is varied to compensate for the light shifting of levels with laser intensity. The corresponding changes in the effective decay rates and the scattering length due to the change in the Rabi frequencies have been taken into account. Dependence of the conversion efficiency on the effective two-photon Raman detuning has also been studied by varying the laser intensity over a narrow range, keeping the two-photon detuning unchanged. The dynamics of the coupled system has been studied in Gross-Pitaevskii and modified Gross-Pitaevskii approaches to demonstrate the effect of the higher order nonlinearity (Lee-Huang-Yang term) with the increase in the laser intensity.