Abstract

We use the gain-feedback approach¹ to explain a number of instabilities observed in sodium vapor with the laser frequency v_L tuned to the defocusing side of line center at v₀. The gain curve, which includes motion of the atoms, predicts two regions of possible gain: Rayleigh gain for frequencies v just above v_L and Raman gain for v ≅v_L - v_R, where v_R is the on-resonance Rabi frequency; see Fig. 1.² Lasing based on these two gain mechanisms has been seen in three different feedback configurations. The new observations are: Rayleigh-gain lasing with no external mirrors using the distributed feedback of counterpropagating pump beams, Rayleigh-gain lasing without a foreign gas, Raman-gain lasing in a ring cavity (see Fig. 2), and both Rayleigh and Raman lasing using a single feedback mirror.

© 1988 Optical Society of America