A Quasi-classical Model for Delineation of Dynamical States and Chaotic Maps in a Spaser
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A Quasi-classical Model for Delineation of Dynamical States and Chaotic Maps in a Spaser Morteza A. Sharif 1
&
K. Ashabi 2
Received: 14 June 2020 / Accepted: 18 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract 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 Hénon 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. Keywords Surface plasmon . Spaser . Chaos . Quantum dot . Nonlinearity . Feedback
Introduction Spaser is a nanoscale counterpart of the laser in which coherent surface plasmons (SPs) are replaced with the photons. SPs are oscillating entities that can be formed at a metal-dielectric interface or within a 2D material [1–8]. SPs are electrically neutralized and can act as the bosons. They can be intensely localized beyond the diffraction limit of the light. A spaser can thus amplify SPs within the form of correlated trains. In similarity with the laser, spaser requires a gain medium [9–12]. The latter can be provided by a set of quantum dots (QDs) for which the dipole moments are excited by an external driving source or in consequence of the local field enhancement [13, 14]. Then, the stimulated near-field interaction of QDs and * Morteza A. Sharif [email protected] 1
Optics and Laser Engineering Group, Faculty of Electrical Engineering, Urmia University of Technology, Urmia 57155-419, Iran
2
MEAPAC Service, L.L.C. One Research Court Suite 450, Rockville, MD 2850, USA
SPs will result in the spasing mechanism. The concept of spaser promises novel applications in nanophotonics and biomedicine [15–20]. Due to the nanoscopic nature of QDs and SPs, the nonlinear dynamical behavior of spaser should be cognized by a quantum coherence approach. This indeed has been impleme
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