We demonstrate the possibility of significantly enhancing the output charac-teristics of a plasmonic nano-laser (spaser) made of a graphene plasmonic resonator and 3-level gain chromophores by using a coherent electric field to control the dynamics.
We investigate surface plasmon amplification in a silver nanoparticle coupled to an externally driven three-level gain medium and show that quantum coherence significantly enhances the generation of surface plasmons. Surface plasmon amplification by stimulated emission of radiation is achieved in the absence of population inversion on the spasing transition, which reduces the pump requirements. The coherent drive allows us to control the dynamics and holds promise for quantum control of nanoplasmonic devices.
We propose a 2D graphene structure containing atomic ensemble as a platform for implementing nanoscale enhanced coherent interactions of plasmonic fields with resonant atomic systems. We determine the graphene surface plasmon modes, and the properties of its electromagnetic fields, and emphasize the role of graphene sheet separation on the interaction with atomic systems for various dipole orientations and positions between the graphene sheets. We analyze the conditions for implementation of coherent interaction of SP mode with resonant atomic ensembles. By solving the Maxwell-Bloch equations that govern the resonant interaction of surface plasmons with atoms, we derive the modified area theorem, which makes it possible to identify the most common nonlinear patterns in the behavior of plasmons under the studied conditions. We obtain analytical and numerical solutions of the area theorem, and find the possibility of stable propagation of isolated SP pulses of graphene surface plasmon modes at "fractional" pulse area values relative to π. We show that the coherent dynamics of SP fields can be realized in nanoscale design and we highlight the possibilities of using this scheme of coherent dynamics for implementing compact multimode nanoscale quantum memory and its integration with other quantum devices on the proposed platform.
Abstract Quantum coherence and interference offer novel pathways to control light–matter interaction at the atomic scale, with enticing prospects in both fundamental and applied science. Here, we demonstrate coherent control over transient excitation of localized surface plasmon modes of a silver nanosphere adjacent to a quantum coherence medium composed of three-level quantum emitters, using a theoretical approach. We show that quantum interference enables more than two orders of magnitude enhancement in the surface plasmon field generated when the quantum emitters are driven coherently, in comparison to incoherent pumping. Furthermore, under optimal conditions, intense surface plasmon lasing can be induced without population inversion on the spasing transition. Our results open up the possibility of overcoming dissipative losses in plasmonic modes in the transient regime when steady-state population inversion is difficult to achieve due to fast relaxation rates and impractical pumping requirements.