Plasmonic superradiance originates from the plasmon mediated strong correlation that builds up between dipolar emitters coupled to a metal nanoparticle. This leads to a fast burst of emission so that plasmonic superradiance constitutes ultrafast and extremely bright optical nanosources of strong interest for integrated quantum nano-optics platforms. We elucidate the superradiance effect by establishing the dynamics of the system, including all features like the orientation of the dipoles, their distance to the particle and the number of active plasmon modes. We determine an optimal configuration for Purcell enhanced superradiance. We also show superradiance blockade at small distances.
PACS numbers:Introduction. In a seminal work, Dicke discovered that a set of N e atoms radiate collectively when they occupy a subwavelength volume. Their emission is much faster (τ Ne = τ 1 /N e ) and stronger (I Ne = N 2 e I 1 ) than for independent atoms. This so-called superradiance originates from spontaneous phase-locking of the atomic dipoles through a same mode and is very similar to the building of cooperative emission in a laser amplifier [1]. Superradiant emission produces original states of light with applications such as narrow linewidth lasers [2] or quantum memories [3,4]. Single collective excitation of atoms in a nanofiber has been demonstrated [5] and superradiant-like behaviour was suggested in a plasmonics junction [6] or a nanocrystal [7], pushing further integration capabilities of quantum technologies. Putsovits and Shahbazyan identifyed plasmon enhanced collective emission for dipoles coupled to a metal nanoparticle (MNP) [8], considering a classical approach which however cannot describe the Dicke cascade at the origin of the cooperative emission. In this communication, taking benefit from recent advances on quantum plasmonics and open quantum systems [9-17], we derive a quantum approach for plasmonic superradiance and discuss the dy-Γtot/Γ0 325 93 2.7 Γtot/Γ1 -5.74 0.03TABLE I: Bright states with 6 emitters at 20 nm from a 30 nm MNP (ω0 = 2.77 eV). The field lines of LSP1 are superimposed to the brightest configuration. * Electronic address: gerard.colas-des-francs@u-bourgogne.frnamics of cooperative emission with particular attention to the role of the localized surface plasmons (LSP n , where n refer to the mode order).Single excitation superradiance We first consider single excitation superradiance that presents a classical analogue, facilitating the physical representation of the collective process. It reduces to an eigenvalue problem on the dipole moment d (i) of N e emitters located at rwhere G is the Green tensor in presence of the MNP, ω 0 the angular frequency of emission and k 0 = ω 0 /c. Γ 0 is the free-space dipolar decay rate. We assume a Drude behavior ε m (ω) = ε ∞ − ω 2 p /(ω 2 + iγ p ω) with ε ∞ = 6, ω p = 7.90 eV and γ p = 51 meV for silver. all LSPs LSP1 LSP2 LSP3 Γtot/Γ1 5.74 6 3 2.25TABLE II: Brightest states maximizing Γtot/Γ1 and considering single mode MNP response. The field lines ...
