title: Quantifying stochasticity in the dynamics of delay-coupled semiconductor lasers via forbidden patterns.
abstract: We quantify the level of stochasticity in the dynamics of two mutually coupled semiconductor lasers. Specifically, we concentrate on a regime in which the lasers synchronize their dynamics with a non-zero lag time, and the leader and laggard roles alternate irregularly between the lasers. We analyse this switching dynamics in terms of the number of forbidden patterns of the alternate time series. The results reveal that the system operates in a stochastic regime, with the level of stochasticity decreasing as the lasers are pumped further away from their lasing threshold. This behaviour is similar to that exhibited by a single semiconductor laser subject to external optical feedback, as its dynamics shifts from the regime of low-frequency fluctuations to coherence collapse.
authors.affiliation: Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa, Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Tiana-Alsina
authors.forename: Javier M
authors.initials: JM
authors.lastname: Buldú
authors.forename: M C
authors.initials: MC
authors.lastname: Torrent
authors.forename: Jordi
authors.initials: J
authors.lastname: García-Ojalvo
mesh_terms: D004581:Electronics; D054023:Lasers, Semiconductor; D015233:Models, Statistical; D009991:Oscillometry / Q000706:statistics & numerical data; D013269:Stochastic Processes; D013598:Systems Theory; D013997:Time Factors