Dynamical characterization of chaotic itinerancy in a three-mode laser subjected to frequency-shifted optical feedback

Spontaneous exchange of leader-laggard relationship in mutually coupled synchronized semiconductor lasers

We investigate the instantaneous behavior of synchronized temporal wave forms in two mutually coupled semiconductor lasers numerically and experimentally. The temporal wave forms of two lasers are synchronized with a propagation delay time, with one laser oscillating in advance of the other, known as the leader-laggard relationship. The leader-laggard relationship can be determined by measuring the cross-correlation between the two temporal wave forms with the propagation delay time. The leader can be identified when the optical carrier frequency of the leader laser is higher than that of the other laser. However, spontaneous exchange between the leader and laggard lasers can be observed in low-frequency fluctuations by short-term cross-correlation measurements, even for a fixed initial optical frequency detuning. The spontaneous exchange of the leader-laggard relationship originates from alternation of partial optical frequency locking between the two lasers. This observation is analyzed using a phase space trajectory on steady-state solutions for mutually coupled lasers with optical frequency detuning.

Chaos synchronization among orthogonally polarized emissions in a dual-polarization laser

We report on the experimental observations of chaos synchronizations among orthogonally polarized emissions in a dual-polarization laser. With a three-mode scheme with a single mode in one polarization and two modes in orthogonal polarizations, synchronization was achieved by the cross-saturation dynamics of population inversions when one of the dual-polarized emissions was subjected to external perturbations, i.e., self-mixing modulation or optical fiber feedback. In-phase synchronization or lag synchronization among orthogonally polarized emissions was achieved depending on the degree of cross saturation in the self-mixing modulation. Synchronization of random bursting was observed in the fiber feedback, in which two chaotic-spiking modes in one polarization with anticorrelated intensity variations synchronize the remaining mode in the orthogonal polarization cooperatively with their total intensity variation. Information sender-mediator-receiver relationships among modes, which represent the dynamical roles of individual modes for establishing the observed three types of collective synchronizations, were identified in terms of an information circulation analysis.