Comparison of metastability-exchange optical pumping sources

Abstract

The efficiencies of two ytterbium (Yb) fiber lasers for metastability-exchange optical pumping are compared with that of an arc-lamp-pumped neodymium-doped lanthanum magnesium hexaluminate laser. Specifically, we report a careful comparison of the 3He nuclear polarizations and polarization rates obtained with each laser, which were carried out for three sealed glass cells filled with low-pressure 3He or 3He–4He mixtures. The two Yb systems are (1) a 1083-nm diode oscillator coupled to a Yb-doped fiber amplifier and (2) an all-fiber system consisting of a Yb-doped fiber oscillator followed by a Yb-doped fiber amplifier. Essentially no difference was observed between the efficiency of the neodymium-doped lanthanum magnesium hexaluminate laser and the diode/fiber system. In comparison, the all-fiber laser produced a 0%–5% lower polarization and a 0%–35% lower polarization rate than the other two lasers, depending upon the specific experimental conditions. Absorption and spectral line-shape measurements suggest that this difference can be attributed to the spectral linewidth of the particular all-fiber laser that was tested.