Abstract

Optical pumping is an efficient method for creating nuclear polarization M in a gas of ³He. M is first achieved in the metastable 2³S state and then transfered to the ground state. Polarized ³He has numerous applications: quantum fluids, precision magnetometry, nuclear targets, etc. Much progress in achieving high values of M has resulted from the development of efficient IR lasers capable of exciting the 2³S–2³P³He transition at 1.08 μm. Using a novel lamp pumped LNA laser delivering 5 W cw, we have achieved M >85% for samples in the torr pressure range. To measure M we have developed an accurate technique based on the change as a function of M of the ratio between σ and π polarized light absorbed from a weak; probe beam by the 2³S metastable atoms. The probe was delivered by a single mode tunable diode pumped LNA laser that was frequency modulated by using an étalon mounted on a galvoplate. M was also measured by monitoring the circular polarization of the 668 nm line emitted by the dis charge. Experimental and theoretical results on the optimization of the pumping will be presented, and the laser systems will be discussed.

© 1992 Optical Society of America