A Quasi-classical Model for Delineation of Dynamical States and Chaotic Maps in a Spaser

In this study, a quasi-classical model is proposed and developed for a surface plasmon (SP) nanolaser (spaser) system. The system is assumed to be composed of two-level quantum dots (QDs) coupled with a/an damping/amplifying cavity. Giving the both stable and unstable states, it is shown that the proposed model can describe the system nonlinear dynamics with an easier and more practical manner in comparison with the fully quantum-based models. Simulation results reveal that the instability in the system dynamical states can initiate in accordance with Ikeda map (as the universal map of instability in many optical systems) but does not progress accordingly. Instead, Duffing map and Henon map are recognized as the two characteristic maps of instability and chaos in the spaser system. More importantly, it is deduced that the SPs’ damping amplitude can be compensated if the feedback depth/nonlinear coefficient becomes as high/large as to induce chaotic regime in the transitional states between the two levels of QDs. A spaser with stimulated SPs can then be launched. Finally, an experimental evidence of a route to chaos is given in a nonlinear medium containing the flakes of reduced graphene oxide (RGO), dispersed inside a dielectric host to indicate the crucial role of feedback depth and nonlinearity. The proposed model can pave the way for designing the spaser systems in a practicable manner.