Instabilities and routes to chaos in a homogeneously broadened 1- and 2-mode ring laser.

A bidirectionally emitting ring laser (/sup 15/NH/sub 3/ at 376-..mu..m wavelength) exhibits self-pulsing and chaos. The routes to chaos are found to be either a one-frequency--period-doubling route to chaos, or a one-frequency--two-frequencies--phase-locking-- period-doubling route to chaos: windows within the chaotic range, the same as reported for a two-roll Benard convection cell experiment. In single-mode operation an instability is observed under conditions compatible with the Lorenz model.