Room-Temperature Coupling of Single Photon Emitting Quantum Dots to Localized and Delocalized Modes in a Plasmonic Nanocavity Array

Abstract

Single photon sources, especially those based on solid state quantum emitters, are key elements in future quantum technologies. What is required is the development of broadband, high quantum efficiency, room temperature, single photon sources, which can also be tunably coupled to optical cavities, which could lead to the development of all-optical quantum communication platforms. In this regard, the deterministic coupling of single photon sources to plasmonic nanocavity arrays has a great advantage due to a long propagation length and delocalized nature of surface lattice resonances. Guided by these considerations, we report experiments on the room temperature tunable coupling of single photon emitting colloidal quantum dots (CQDs) to localized surface plasmon and surface lattice resonance modes in plasmonic nanocavity arrays. Using a time-resolved photoluminescence measurement on isolated CQD, we report the significant advantage of surface lattice resonances in realizing a much higher Purcell effect, despite the large dephasing of CQDs, with values of ∼22 and ∼6 for coupling to the lattice and localized modes, respectively. We present measurements on the antibunching of CQDs coupled to these modes with g(2)(0) values in the quantum domain, providing evidence for effective cooperative behavior. We present a density matrix treatment of the coupling of CQDs to plasmonic and lattice modes enabling us to model the experimental results on Purcell factors as well as on the antibunching. We also provide experimental evidence of indirect excitation of remote CQDs mediated by the lattice modes and propose a model to explain these observations. Our study demonstrates the possibility of developing nanophotonic platforms for single photon operations and communications with broadband quantum emitters and plasmonic nanocavity arrays since these arrays can generate entanglement between spatially separated quantum emitters.