Laser cooling of unbound atoms in nondissipative optical lattices

TL;DR

This paper analyzes laser cooling of unbound atoms in nondissipative optical lattices using semiclassical theory, revealing mechanisms similar to Doppler and Sisyphus cooling depending on transition strength, and provides analytical expressions for cooling coefficients.

Contribution

It introduces a semiclassical approach to understand cooling mechanisms in nondissipative optical lattices, connecting them to known Doppler and Sisyphus processes, with analytical results for key parameters.

Findings

Cooling mechanisms depend on Raman transition strength.

Analytical expressions for friction and diffusion coefficients are derived.

Kinetic temperature estimates are provided.

Abstract

The semiclassical theory of laser cooling is applied for the analysis of cooling of unbound atoms with the values of the ground and exited state angular moments 1/2 in a one-dimensional nondissipative optical lattice. We show that in the low-saturation limit with respect to the pumping field a qualitative interpretation of the cooling mechanisms can be made by the consideration of effective two-level system of the ground-state sublevels. It is clarified that in the limit of weak Raman transitions the cooling mechanism is similar to the Doppler mechanism, which is known in the theory of two-level atom. In the limit of strong Raman transitions the cooling mechanism is similar to the known Sisyphus mechanism. In the slow atom approximation the analytical expressions for the coefficients of friction, spontaneous and induced diffusion are given, and the kinetic temperature is estimated.