Raman-Nath and Bragg scattering in atomic deflection

A combined analytical/numerical study of atomic deflection from a standing-wave light field that incorporates both the Bragg and Raman-Nath scattering regimes as extremes has been conducted. The numerical approach uses a variant of the beam propagation method (BPM). By using the BPM it is possible to stimulate atomic scattering without having to assume the number of scattered beams and, therefore, to investigate the transition between the Raman-Nath and Bragg scattering regimes. The results show that the various scattering regimes can be characterized in terms of a few dimensionless parameters of the system. In addition, the BPM allows the study of a finite velocity spread in the incident atomic and of its potential detrimental effect on the atomic scattering, particularly in an atomic interferometer. Analytical results show a very close correspondence between atomic deflection and acoustooptic deflection. In the general case, atomic deflection is analogous to light scattering from a birefringent grating. If the atomic frequency is significantly detuned from the laser, the analogy is with an isotropic grating.