Plasmonic Cavities and Individual Quantum Emitters in the Strong Coupling Limit.

Content Provider	Europe PMC
Author	Bitton, Ora Haran, Gilad
Copyright Year	2022
Abstract	ConspectusThe interaction of emitters with plasmonic cavities (PCs) has beenstudied extensively during the past decade. Much of the experimentalwork has focused on the weak coupling regime, manifested most importantlyby the celebrated Purcell effect, which involves a modulation of thespontaneous emission rate of the emitter due to interaction with thelocal electromagnetic density of states. Recently, there has beena growing interest in studying hybrid emitter-PC systems in the strong-coupling(SC) regime, in which the excited state of an emitter hybridizes withthat of the PC to generate new states termed polaritons. This phenomenonis termed vacuum Rabi splitting (VRS) and is manifested in the spectrumthrough splitting into two bands.In this Account, we discussSC with PCs and focus particularlyon work from our lab on the SC of quantum dots (QDs) and plasmonicsilver bowtie cavities. As bowtie structures demonstrate strong electricfield enhancement in their gaps, they facilitate approaching the SCregime and even reaching it with just one to a few emitters placedthere. QDs are particularly advantageous for such studies, due totheir significant brightness and long lifetime under illumination.VRS was observed in our lab by optical dark-field microspectroscopyeven in the limit of individual QDs. We further used electron energyloss spectroscopy, a near-field spectroscopic technique, to facilitatemeasuring SC not only in bright modes but also in subradiant, darkplasmonic modes. Dark modes are expected to live longer than brightmodes and therefore should be able to store electromagnetic energyfor longer times.Photoluminescence (PL) is another useful observablefor probingthe SC regime at the single-emitter limit, as shown by several laboratories.We recently used Hanbury Brown and Twiss interferometry to demonstratethe quantum nature of PL from QDs within PCs, verifying that the measurementsare indeed from one to three QDs. Further spectroscopic studies ofQD-PC systems in fact manifested several surprising features, indicatingdiscrepancies between scattering and PL spectra. These observationspointed to the contribution of multiple excited states. Indeed, usingmodel simulations based on an extended Jaynes–Cummings Hamiltonian,it was found that the involvement of a dark state of the QDs can explainthe experimental findings. Given that bright and dark states coupleto the cavity with different degrees of coupling strength, the PCaffects in a different manner each excitonic state. This yields complexrelaxation pathways and interesting dynamics.Future work shouldallow us to increase the QD-PC coupling deeperinto the SC regime. This will pave the way to exciting applicationsincluding the generation of single-photon sources and studies of cavity-inducedcoherent interactions between emitters.
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ISSN	00014842
Journal	Accounts of Chemical Research [Acc Chem Res]
Volume Number	55
DOI	10.1021/acs.accounts.2c00028
PubMed Central reference number	PMC9219108
Issue Number	12
PubMed reference number	35649040
e-ISSN	15204898
Language	English
Publisher	American Chemical Society
Publisher Date	2022-06-01
Access Restriction	Open
Rights License	Permits the broadest form of re-use including for commercial purposes, provided that author attribution and integrity are maintained (https://creativecommons.org/licenses/by/4.0/). © 2022 The Authors. Published by American Chemical Society
Content Type	Text
Resource Type	Article
Subject	Chemistry Medicine