Simulations of Sisyphus cooling including multiple excited states

TL;DR

This paper extends laser cooling theory to include multiple excited hyperfine states, using classical external degrees of freedom and quantum internal states, to explain experimental temperature dependencies in optical lattices.

Contribution

It introduces a simulation approach that incorporates multiple excited states, resolving discrepancies between theory and experiments regarding temperature dependence.

Findings

Temperature depends on detuning, not just lattice depth.

Simulations match experimental temperature variations.

Multiple excited states influence cooling limits.

Abstract

We extend the theory for laser cooling in a near-resonant optical lattice to include multiple excited hyperfine states. Simulations are performed treating the external degrees of freedom of the atom, i.e., position and momentum, classically, while the internal atomic states are treated quantum mechanically, allowing for arbitrary superpositions. Whereas theoretical treatments including only a single excited hyperfine state predict that the temperature should be a function of lattice depth only, except close to resonance, experiments have shown that the minimum temperature achieved depends also on the detuning from resonance of the lattice light. Our results resolve this discrepancy.