Multistate intermittency on the route to chaos of a semiconductor laser subjected to optical feedback from a long external cavity

International audienceWe observe experimentally two regimes of intermittency on the route to chaos of a semiconductor laser subjected to optical feedback from a long external cavity as the feedback level is increased. The first regime encountered corresponds to multistate intermittency involving two or three states composed of several combinations of periodic, quasiperiodic, and subharmonic dynamics. The second regime is observed for larger feedback levels and involves intermittency between period-doubled and chaotic regimes. This latter type of intermittency displays statistical properties similar to those of on-off intermittency. Published by AIP Publishing. https://doi.org/10.1063/1.5013332 Irregular switching between dynamical regimes, or, intermittency, is a ubiquitous phenomenon observed in many nonlinear systems when a parameter of the system approaches a critical point. External-cavity lasers (ECLs) exploit an external mirror to provide time-delayed optical feedback into the laser diode. Their dynamics can be high-dimensional and highly multistable; thus, ECLs are interesting testbeds to observe and understand transitions between attractors and the involved timescales. Despite the existence of several reports on intermittency in ECLs, there is still a lack of knowledge in the important case in which the laser is biased well above its threshold. We observe in this case two distinct intermit-tency regimes on the route to chaos, as the feedback strength is increased. The first regime corresponds to multistate intermittency involving two or three states composed of several combinations of periodic, quasiperi-odic, and subharmonic dynamics. The second regime is observed for larger feedback levels and involves intermit-tency between period-doubled and chaotic regimes