Core-shell multilayered nanoparticles: giant photonic density of states coupled to the far-field

We present a quantum theoretical treatment of light-matter coupling in the system consisting of a quantum dot and a spherical core-shell metal-dielectric multilayer nanoparticle. It is shown that both weak and strong coupling regimes can be realized in the set-up. Specifically, we demonstrate a strong coupling regime between a quantum dot and a nanoparticle, when the quantum dot resonance is tuned to the frequency at which normal component of effective nanoparticle permittivity is crossing zero. Moreover, we demonstrate the regime at which the quantum dot decays much faster than in vacuum (due to the large Purcell factor) and at the same time radiates more power to the far field. This findings pave the way towards more efficient control over radiation properties of quantum emitters.