Scaling Law in Laser Cooling on Narrow-Line Optical Transitions

TL;DR

This paper investigates laser cooling of atoms with narrow-line optical transitions, revealing quantum effects that differ from classical Doppler cooling theories and introducing parameters for optimizing cooling in atomic clock applications.

Contribution

It introduces a set of dimensionless parameters to analyze laser cooling dynamics and demonstrates the significant quantum recoil effects in narrow-line transitions.

Findings

Minimum cooling temperature occurs near 3 recoil frequencies for red detuning.

Quantum recoil effects cause deviations from semiclassical Doppler cooling predictions.

Results aid in optimizing laser cooling for atomic clock atoms like Ca, Sr, and Mg.

Abstract

In this paper laser cooling of atoms with a narrow-line optical transition, i.e. in regimes of quantum nature of laser-light interactions resulting in a significant recoil effect, is studied. It is demonstrated that a minimum laser cooling temperature for two-level atom in standing wave reached for red detuning close to 3 recoil frequency greatly different from the theory used for a semiclassical description of Doppler cooling. A set of dimensionless parameters uniquely characterizing the time evolution and the steady state of different atoms with narrow-line optical transitions in the laser field is introduced. The results can be used for analysis of optimal conditions for laser cooling of atoms with narrow lines such as $Ca$, $Sr$, and $Mg$, which are of great interest for atomic clocks.