Abstract

Recent experiments¹ on transverse instabilities in Gaussian laser beams using sodium vapor for the nonlinear medium have shown well-behaved oscillations of the type first proposed by Ikeda.² The period of such oscillations for a medium with infinitely fast response is given by 2τ_r, where τ_R is the time it takes for light to traverse the feedback loop. Our experimental arrangement (Fig. 1) uses a ring dye laser with well-defined transverse properties tuned to a frequency 2 to 10 GHz below the sodium D₂ resonance. Operation on the self-defocusing side guarantees that no self-trapped filaments are formed. A feedback mirror several meters from the sodium sample provides the delay needed for the Ikeda instability.

© 1985 Optical Society of America