Search for Deterministic Chaos in the Mode Switching Instability of the Dye Ring Laser*

The two-mode dye ring laser when operated moderately far above threshold exhibits an instability that causes it to switch seemingly at random between clockwise and counterclockwise modes. The phenomenon has been explained in terms of spontaneous emission fluctuations,1-4 which cause the representative point in phase space to tunnel between two metastable states, and this interpretation has so far proved to be in good agreement with all experimental measurements. By implication the switching phenomenon is a macroscopic manifestation of quantum fluctuations in the laser, and it can be described by two coupled Langevin equations in the two mode amplitudes, with additive quantum noise.1 Although these equations account for the mode switching, better quantitative agreement with experiment is obtained when pumping fluctuations are also introduced.5