Optical trapping of ytterbium atoms

Abstract

This dissertation describes an experimental study on magneto-optical trapping (MOT) of ytterbium atoms. In particular, Doppler cooling and sub-Doppler cooling have been investigated and compared in the same atom, and sub-Doppler cooling has been studied in two isotopes of ytterbium possessing different nuclear angular momenta. Ytterbium offers a unique combination of having a closed S-shell in the ground state, several isotopes with high abundances, and two transitions that are accessible by lasers that can be used for laser cooling and trapping. Laser cooling with several different ground-state angular momenta can be studied by simply changing isotopes with little changes to the experimental parameters.All seven stable isotopes of ytterbium have been slowed from an atomic beam, trapped in a MOT using the strong 1S 0-1P1 line and transfered into a second MOT using the 1S0- 3P1 intercombination line. The apparatus developed for this experiment is described in detail, including the lasers used for both transitions at 399 nm and 556 nm. Trap properties such as temperature, spring constant, lifetime of the traps, and isotope dependence of cooling mechanisms in the 1S0- 3P1 trap were investigated. Doppler cooling was studied in even isotopes with no spin in the ground state. Sisyphus cooling in the ground state of odd isotopes of alkaline-earth-like atoms with zero electronic and non-zero nuclear angular momentum was demonstrated for the first time, and compared with numerical simulations. Future directions that exploit the unique features of ytterbium are also discussed.