Abstract
A bidirectionally emitting ring laser (15 NH3 at 376-μm wavelength) exhibits self-pulsing and chaos. The routes to chaos are found to be either a one-frequencyperiod-doubling route to chaos, or a one-frequencytwo-frequenciesphase-locking period-doubling route to chaos: windows within the chaotic range, the same as reported for a two-roll Bénard convection cell experiment. In single-mode operation an instability is observed under conditions compatible with the Lorenz model.