Abstract

Recent advances in laser cooling and trapping have led to a growing interest in laser spectroscopy in cold atomic samples. Examples include the work of Guo et al.¹ and Courtois et al.² about the recoil-induced resonance, and Bonifacio et al.⁵ and Moore et al.⁴ about the collective-atomic-recoil lasers (CARL). At the heart of these applications is the atomic recoil by photon absorption and emission. In this work, we explore a recoil-related phenomenon: hole burning resulting from the momentum redistribution of atoms by spontaneous emission, and its possible application in the precision spectroscopy. In the traditional saturation spectroscopy, the hole in the Doppler profile is created by laser excitation of atoms from the ground to the excited level. By contrast, the hole, in this work, is produced by removing the atoms in the velocity group, where the hole is burned, into the neighboring velocity groups of the same ground level. This process is accomplished through optical pumping and momentum redistribution by spontaneous emission. As a result, the requirement on the intensities of the driving laser fields is low, limited only by the interaction time. This is in contrast to the traditional saturation spectroscopy where the driving laser intensity has to be comparable to the saturation intensity determined by the decay rate of the excited level.

© 1999 Optical Society of America