Use of Broadened Diode Lasers to Enhance Optical Pumping of Alkali Metals

We have made a systematic study of rubidium optical pumping using an amplified tunable diode laser which has been incrementally broadened in order to determine the effect of linewidth broadening on rubidium polarization. We vary the frequency of the circularly-polarized laser across the D$_{\mathrm{1\thinspace }}$transition absorption profile for each of four linewidths (unbroadened (.01 MHz), .5 MHz, 2 GHz, and 8 GHz) and measure the rubidium polarization using Faraday rotation. The rubidium number density is on the order of 10$^{\mathrm{12\thinspace }}$cm$^{\mathrm{-3}}$, with 1 Torr of N$_{\mathrm{2\thinspace }}$as the buffer gas. These results are then compared with polarization measurements taken using a re-pump laser tuned to the rubidium D$_{\mathrm{2}}$ transition, and with theoretical calculations of the rubidium polarization.