Spin-exchange optical pumping using a frequency-narrowed high power diode laser

We describe a method for frequency narrowing commercial high power diode lasers from 2 to 0.1 nm bandwidth with modest loss of power (<2 dB). The resulting laser light is well suited for spin-exchange optical pumping, and we demonstrate that the polarization produced by a 2.5 W narrowband laser exceeds that of a 15 W array by 40% in our optical pumping system.