Quasiperiodic fluctuations and chaos in a gas-discharge laser with active mode locking

An experimental investigation was made of the processes occurring on transition from active mode locking to chaotic free running of an He–Ne laser (1.15 μm). The appearance of quasiperiodic fluctuations and chaos was due to the formation of supermodes observed experimentally. A reduction of the depth of modulation induced higher supermodes. An asymmetry of the bifurcation diagram was observed as a result of a change in the sign of the mismatch between the modulation and beat frequencies. The nature of the processes occurring as a result of suppression of mode locking was fairly complex, but the following bifurcations could be identified: period doubling, tangential bifurcation, appearance of tori. A mapping relationship was obtained to describe changes in the pulse profile from one pass to the next during propagation in the laser resonator.