Optical pumping in He-4* with frequency-shifted feedback amplification of light

We use a frequency-shifted feedback technique with a high-gain fiber amplif ier operating at lambda = 1083 nm to produce a multifrequency light beam th at covers a controllable spectral range. It is ideal for optically pumping a gas of metastable He because it spans the Doppler width, and its high eff iciency has implications for many applications. Measurements confirm that e ight times fewer atoms are left in the unchosen states with multifrequency light. (C) 2000 Optical Society of America [S0740-3224(00)00304-0] OCIS cod es: 140.0140, 140.5560, 190.2640, 060.2320, 170.3880.