Sodium Raman laser: direct measurements of the narrow-band Raman gain

Using a sodium Raman laser that is pumped by a single-frequency cw dye laser, we have measured the narrow-band Raman gain that exists in the vicinity of the sodium D(1) line. Large gains (>10 cm(-1)) are measured at moderate pump intensities and sodium densities. The high gain allows us to detect directly a 1.772-GHz beat on the pump beam after it makes only a single pass through the sodium cell. By scanning the frequency of the sodium Raman laser while keeping the pump intensity and frequency constant, we are able to map out the Raman gain profile. The narrowness of the Raman gain is consistent with the narrow beat signal between the Raman-laser beam and the pump beam that was reported earlier [Opt. Lett. 16, 1853 (1991)].