Effects of nonlinearity on the optical diffraction of Bose-Einstein condensates: Direct integration of optically coupled multicomponent Gross-Pitaevskii equation

Abstract

We investigate in detail the effects of nonlinearity on optical diffraction of Bose-Einstein condensates (BECs). By directly integrating the optically coupled two-component Gross-Pitaevskii equation in real space-time, comprehensive analyses of BEC optical diffraction phenomena are done under various conditions of light-pulse irradiation, total number of BEC atoms, etc., without using the adiabatic elimination approximation for an atomic excited state. Calculation results for the optical diffraction of {sup 87}Rb BECs revealed that (1) the effect of nonlinearity on the atomic states causes the ''nonkinetic'' nonlinear effect in the Raman-Nath regime of diffraction, while the dynamics of BEC atoms due to the nonlinearity-induced repulsive forces works dominantly to produce the ''kinetic'' nonlinear effect in the Bragg regime of diffraction; (2) nonlinearity reduces the amplitude and frequency of the two-photon Rabi oscillation between BEC stationary and moving states, suggesting limitations in implementing the BEC Mach-Zehnder interferometer; and (3) the observed nonlinear effects are free from kinetic effects of the atomic excited state and not responsible for the optical transition process.