Classical Laser Cooling and Trapping

The study of atomic quantum behavior requires that atoms be in a low energy, low temperature state such that their behavior is dominated by quantum effects rather than classical. Investigating quantum behaviors of atoms requires the ability to cool and trap atoms to an ultracold regime near 0 K. This is achievable by using optical forces from atomic interactions with a laser beam to slow atoms. Despite being a fundamentally quantum system, the process of laser cooling and trapping can be accurately described classically. This paper presents the classical theory of laser trapping and cooling by studying atomic interaction with photons and the resulting optical forces. Then, the mechanics of the ubiquitous laser cooling method known as Doppler cooling are derived. Finally, trapping methods to confine cooled atoms using magneto-optical traps and dipole force traps as well as some experimental considerations are discussed