Abstract
A modified rate equation model was presented to theoretically investigate the nonlinear dynamics of solitary two-state quantum dot lasers (TSQDLs) under optical feedback. The simulated results showed that, for a TSQDL biased at a relatively high current, the ground-state (GS) and excited-state (ES) lasing of the TSQDL can be stimulated simultaneously. After introducing optical feedback, both GS lasing and ES lasing can exhibit rich nonlinear dynamic states including steady state (S), period one (P1), period two (P2), multi-period (MP), and chaotic (C) state under different feedback strength and phase offset, respectively, and the dynamic states for the two lasing types are always identical. Furthermore, the influences of the linewidth enhancement factor (LEF) on the nonlinear dynamical state distribution of TSQDLs in the parameter space of feedback strength and phase offset were also analyzed. For a TSQDL with a larger LEF, much more dynamical states can be observed, and the parameter regions for two lasing types operating at chaotic state are widened after introducing optical feedback.
Highlights
Chongqing City Key Laboratory of Micro & Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, China; School of Mathematics and Physics, Jingchu University of Technology, Jingmen 448000, China
Based on the three-level model, after referring to the optical feedback processing methods in Ref. [48], we propose modified rate equations for describing the nonlinear dynamics of two-state quantum dot lasers (TSQDLs) under optical feedback as follows: dNW L
For a TSQDL biased at 120 mA, both GS and ES lasing could be stimulated simultaneously, and the output power of GS emission was slightly larger than that of ES emission
Summary
The theoretical model in this work was based on the three-level model of QD lasers, which has been adopted to analyze the static and dynamic behaviors, noise characteristics of QD lasers operating at free-running [42,43], and the small-signal modulation response and relative intensity noise of QD lasers under optical injection-locking conditions [44]. QD lasers (TSQDLs) based on the three-level model [45]. In this system, two relatively low energy levels involving ground state (GS) and the first excited state (ES) were taken into account. The rest of the carriers recombined spontaneously with a time τ spon. For the carriers in ES, some of them relaxed into GS with a relaxation time τGS spon other carriers recombined spontaneously with an emission time τES. ES spon some carriers recombined spontaneously with an emission time τGS. Based on the three-level model, after referring to the optical feedback processing methods in Ref. Where WL, ES, GS are the wetting layer, excited-state, and ground-state, respectively, and the superscript spon represents the spontaneous emission.
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