The extreme spatial light confinement provided by graphene plasmons is anticipated to facilitate strong light-matter coupling through their resonant interaction with proximal quantum emitters [1], as well as to push the remarkably-high intrinsic nonlinear response of the carbon layer to record-high levels [2]. Plasmon resonance frequencies in graphene typically lie in the infrared and terahertz regimes, which is ideal for probing the vibrational fingerprints of nanometric biomolecules [3], but energetically mismatched from the transitions of robust, solid-state single-photon sources such as quantum dots and nitrogen-vacancy centers. Here we propose to utilize the near-field generated by the nonlinear optical response of resonantly-driven localized graphene plasmons to achieve strong coupling with proximal quantum emitters. Specifically, we predict that the near fields produced through mid-infrared driven plasmon-assisted third-harmonic generation in a doped graphene nanodisk are sufficiently large as to yield observable Rabi splitting in two- or multi-level quantum emitters operating in the near-infrared regime. In this scenario, the electrostatic tunability of graphene plasmon resonances can be exploited first to target the relevant electronic transition of a particular quantum emitter and later to actively control its absorption and radiative emission. We envision potential applications for the proposed nonlinear graphene plasmon-assisted strong coupling scheme in nonlinear sensing and as actively-controllable elements in quantum information networks.
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