Plasmonic Cavity Coupling

Abstract

The large losses of plasmonic nanocavities, orders of magnitude beyond those of photonic dielectric cavities, places them, perhaps surprisingly, as exceptional enhancers of single emitter light-matter interactions. The ultra-confined, sub-diffraction limited, mode volumes of plasmonic systems offer huge coupling strengths (in the 1-100 meV range) to single quantum emitters. Such strengths far outshine the lower coupling strengths of dielectric microcavities, which nonetheless easily achieve single emitter 'strong coupling' due to the low loss rates of dielectric cavities. In fact, it is the much higher loss rate of plasmonic cavities that make them desirable for applications requiring bright, fastemitting photon sources. Here we provide a simple method to reformulate lifetime measurements of single emitters in terms of coupling strengths to allow a useful comparison of the literature of plasmonic cavities with that of cavity-QED, typically more closely associated with dielectric cavities. Using this approach, we observe that the theoretical limit of coupling strength in plasmonic structures has almost been experimentally achieved with even single molecule strong coupling now observed in plasmonic systems. However, key problems remain to maximise the potential of plasmonic cavities, including precise and deterministic nanopositioning of the emitter in the nanosized plasmonic mode volumes, understanding the best geometry for the plasmonic cavity, separating useful photons from background photons and dealing with the fluorescence quenching problems of metals. Here we attempt to raise awareness of the benefits of plasmonic nanocavities for cavity-QED and tackle some of the potential pitfalls. We observe that there is increasing evidence, that using correct geometries, and improving emitter placement abilities, significant quenching can be avoided and photon output maximised towards the extraordinary limit provided by the high radiative rates of plasmonic nanocavities.

Strong Light–Matter Interactions Enabled by Polaritons in Atomically Thin Materials

“…Let us consider a plasmonic resonator—e.g., an individual metallic nanoparticle supporting a LSPR—in close proximity to an emitter such that there is significant overlap between the near‐fields of the plasmonic cavity and of the emitter. If the emitter is well described by a point‐like two‐level system (Figure a), then the coupling energy follows from , where is transition dipole moment associated with the transition and is the electric field evaluated at the emitter's position . In this review, we shall consider that the “emitter” is represented by an excitonic resonance ascribed to the 2D TMDC (Figure b); in such a case, the previous expression cannot be employed directly and an explicit formula for the coupling energy is in general a nontrivial and onerous task (for a discussion about this predicament, see, for instance, ref.…”

“…If the emitter is well described by a point-like two-level system (Figure 12a), then the coupling energy follows from ( ) 0 g E E r r µ = ⋅ , where µ is transition dipole moment associated with the transition and ( ) 0 E E r r is the electric field evaluated at the emitter's position 0 r r . [197,214,215,217] In this review, we shall consider that the "emitter" is represented by an excitonic resonance ascribed to the 2D TMDC ( Figure 12b); in such a case, the previous expression cannot be employed directly and an explicit formula for the coupling energy is in general a nontrivial and onerous task (for a discussion about this predicament, see, for instance, ref. [220] and references therein).…”

Electron transfer in confined electromagnetic fields

“…Below we show results for two parameter sets associated with different cavities. First, recent reports[76][77][78][79][80] indicate that a single molecule splitting of order  ~ 100meV…”

Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities: an overview on properties and applications [Invited]

“…It is clear that harnessing light and spins through plasmons at the nanoscale may eventually lead to more effective ways to process and store information with photons and create different types of steerable optical elements with the outstanding ability typical of the human eye to adapt to changes and fluctuations in light characteristics. Many paths have still to be explored, first of all the use of exotic or non-conventional plasmonic modes such as optical anapoles [ 197 , 198 ], cavity [199,200] or dark modes [201][202][203] to push magneto-optical effects in magnetic metamaterials to their limits on the nanoscale. Moreover, the works on magneto-plasmonic crystals reported so far are all at normal incidence, while it is known that excitation of SLRs using both the inplane and out-of-plane polarizations of the incident light brings interesting perspectives, such as the generation of high quality SLRs [ 204 ].…”