N. P. Bigelow

Forces on three-level atoms including coherent population trapping

We present a calculation of the force on a stationary three-level atom excited by a nearly resonant Raman light field, which may be composed of an arbitrary combination of standing- and traveling-wave fields. The effects of the ground-state coherences are explicitly included and are shown to play a crucial role in the nature of the force on the atom. We show that the force contains terms that vary on length scales both shorter and longer than the optical wavelength and that the magnitude of these terms can be made arbitrarily large.

Cooling and Trapping of Three-level Atoms in a Bichromatic Standing Wave

We show that a three-level atom in the cascade configuration can be stably trapped and cooled in one dimension by an intense bichromatic standing wave. At the two-photon resonance, rectified dipole forces result in a deep potential well which can be used to localize the atoms in space. In the vicinity of the rectified potential minimum, the spatial dependence of the dressed state energies can lead to a velocity dependence of the force which produces damping of the atomic motion. Consideration of the heating effects of momentum diffusion indicates that cooling and stable trapping at low temperatures is possible in such a bichromatic field.

Optical force on the Raman dark state in two standing waves

Abstract We use the normal modes of atom-field coupling to explain the force of a three-level (Λ) atom excited by two standing wave optical fields. An expression for the force in the weak field, small detuning limit is derived by inspection, and shown to agree with the exact solution to the optical Bloch equations. We describe the physical origin of the completely rectified force components as well as components which vary on scales much narrower than the optical wavelength. We emphasize the importance of the force component associated with the “dark state” and discuss the influence of the phase difference between the fields.

Phase-dependent velocity selective coherent population trapping in a folded three-level ([and ]) system under standing wave excitation

Abstract Theoretically identified are the conditions under which velocity selective coherent population trapping (VSCPT) takes place when a three-level [and ] system is excited by a pair of Raman resonant standing waves. The efficiency of the VSCPT depends on the relative phase, Φ, between the standing waves, and vanishes when Φ = 0. Also reviewed are previous experimental observations by Aspect et al. [Phys. Rev. Lett. 61 (1988) 826] which qualitatively validate the predictions. Finally, the implication of this result to the feasibility of a dense trap of sub-recoil temperature [and ] atoms is discussed.

Grating Enhanced Gain and Reverse Oscillations in a Sodium Vapor Laser: Evidence for Collective Atomic Recoil Lasing (CARL)

The collective atomic recoil laser has recently been proposed as a very efficient method for generation of high frequency radiation such as x-rays and gamma rays and has been described as sharing the properties of both atomic and free electron lasers.

Anisotropic velocity-dependent vortex forces: two-level atoms in two-dimensional standing waves

We consider the velocity-dependent light pressure force on a two-level atom interacting with a two-dimensional nearly resonant standing-wave light field. We show that there can be anisotropic cooling-heating forces that will cool the atoms along one field axis while heating them along the perpendicular axis. The force is identified as a spontaneous vortex force associated with the local traveling-wave character of the two-dimensional field. We provide a simple interpretation of this anomalous force in terms of the interplay between the vortical momentum flow of the light field and a motion-induced population transfer between the ground and excited atomic states.