Abstract

Theoretical calculations are presented for the probe absorption spectra of atoms having ground-state angular momentum J_g=1 that are subjected to weak pump fields that produce spatial polarization gradients. The pump fields are σ⁺ - σ⁻ polarized, and the probe is σ⁻ polarized, copropagating with the σ⁺ pump. Under conditions typical of sub-Doppler cooling, and in the limit that the pump-probe detuning is much larger in amplitude than is the atomic excited- state decay rate, there are mainly two contributions to the spectra. One is the Raman signal, which is associated with transitions between ground-state sublevels with different populations and energy shifts induced by the pump fields. The other contribution, which has not been considered before to our knowledge, is the recoil-induced signal, originating from the atomic recoil that occurs on the absorption or emission of radiation by the atom.

© 1993 Optical Society of America