Room temperature tunable coupling of single photon emitting quantum dots to localized and delocalized modes in plasmonic nanocavity array

TL;DR

This paper demonstrates room temperature tunable coupling of colloidal quantum dots to plasmonic nanocavity arrays, achieving high Purcell factors and effective single-photon emission, advancing quantum photonic technologies.

Contribution

It reports the experimental realization of tunable coupling of quantum dots to plasmonic modes with high Purcell enhancement and models the interactions, enabling development of nanophotonic quantum platforms.

Findings

High Purcell factors (~22 and ~6) achieved for lattice and localized modes.

Evidence of antibunching indicating quantum single-photon emission.

Indirect excitation of remote quantum dots via lattice modes demonstrated.

Abstract

Single photon sources (SPS), 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 SPS which can also be tunably coupled to optical cavities which could lead to development of all-optical quantum communication platforms. In this regard deterministic coupling of SPS to plasmonic nanocavity arrays has great advantage due to long propagation length and delocalized nature of surface lattice resonances (SLRs). Guided by these considerations, we report experiments on the room temperature tunable coupling of single photon emitting colloidal quantum dots (CQDs) to localised and delocalised modes in plasmonic nanocavity arrays. Using time-resolved photo-luminescence measurement on isolated CQD, we report significant advantage of SLRs in realizing much higher Purcell effect, despite large dephasing of CQDs, with values of ~22 and ~ 6 for coupling to the lattice and localised modes, respectively. We present measurements on the antibunching of CQDs coupled to these modes with g(2)(0) values in quantum domain providing evidence for an 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 to spatially separated quantum emitters.