We have studied laser optical pumping of Rb at densities up to 4×${10}^{14}$ atoms/${\mathrm{cm}}^3$ and produced polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ by spin exchange with Rb. Numerical calculations show that for a high-density Rb vapor GaAlAs diode laser arrays can provide results similar to those obtained with a broadband ${\mathrm{Kr}}^{+}$-ion–dye-laser system. We have confirmed these calculations with measurements using a 40-GHz full width at half maximum bandwidth dye laser and 100- and 500-mW GaAlAs diode laser arrays (Spectra Diode Labs Array Nos. SDL-2410C and SDL-2450C). We have optically pumped Rb of density [Rb]=4×${10}^{14}$ atoms/${\mathrm{cm}}^3$, and we have measured up to 70% ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ polarization in a 4-${\mathrm{cm}}^3$ volume with 600 mW from the dye laser. With the diode laser arrays, we have pumped with 30 and 300 mW with results comparable to those obtained with the dye laser. With a 1-W diode laser array, we anticipate 70–80 % ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ polarization in a 4-${\mathrm{cm}}^3$ volume.

• Received 11 July 1989

DOI:https://doi.org/10.1103/PhysRevA.40.4447