Ensemble strong coupling

PublishedJournal Article© 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Strong coupling between light and an ensemble of molecules leads to the formation of new hybrid states and offers the exciting prospect of a new route to control material properties. Now a theoretical model has been introduced to complement the recent observation of strong coupling between the vibrational modes of molecules and an electromagnetic (cavity) mode. This new work by del Pino et al (2015 New J. Phys. 17 053040) makes an important contribution by offering fresh insight into the underlying physics, especially into the role of dephasing processes in determining the dynamics of ensemble strong coupling

Electrically tuneable exciton-polaritons through free electron doping in monolayer WS2_2 microcavities

We demonstrate control over light-matter coupling at room temperature combining a field effect transistor (FET) with a tuneable optical microcavity. Our microcavity FET comprises a monolayer tungsten disulfide WS$_2$ semiconductor which was transferred onto a hexagonal boron nitride flake that acts as a dielectric spacer in the microcavity, and as an electric insulator in the FET. In our tuneable system, strong coupling between excitons in the monolayer WS$_2$ and cavity photons can be tuned by controlling the cavity length, which we achieved with excellent stability, allowing us to choose from the second to the fifth order of the cavity modes. Once we achieve the strong coupling regime, we then modify the oscillator strength of excitons in the semiconductor material by modifying the free electron carrier density in the conduction band of the WS$_2$. This enables strong Coulomb repulsion between free electrons, which reduces the oscillator strength of excitons until the Rabi splitting completely disappears. We controlled the charge carrier density from 0 up to 3.2 $\times$ 10$^{12}$ cm$^{-2}$, and over this range the Rabi splitting varies from a maximum value that depends on the cavity mode chosen, down to zero, so the system spans the strong to weak coupling regimes.Comment: Accepted for publicatio

Localized exciton-polariton modes in dye-doped nanospheres: a quantum approach

We model a dye-doped polymeric nanosphere as an ensemble of quantum emitters and use it to investigate the localized exciton-polaritons supported by such a nanosphere. By determining the time evolution of the density matrix of the collective system, we explore how an incident laser field may cause transient optical field enhancement close to the surface of such nanoparticles. Our results provide further evidence that excitonic materials can be used to good effect in nanophotonics.Comment: 16 pages, 4 figure

Fluorescence enhancement through modified dye molecule absorption associated with the localized surface plasmon resonances of metallic dimers

Copyright © 2008 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. This is the published version of an article published in New Journal of Physics Vol. 10, article 105002. DOI: 10.1088/1367-2630/10/10/105002Nano-antennae consisting of gold particle dimers were fabricated by electron-beam lithography. Dark-field scattering spectroscopy was used to probe the plasmonic response of individual nano-antennae and to characterize the localized surface plasmon resonances they support. Fluorescence from dye molecules dispersed in a thin polymer film that covered the dimers was used to probe the interaction between fluorophores and the nano-antennae. Through a suitable choice of dye emission spectrum and spectral position of the dimer resonance, we were able to focus on the way the plasmon resonances may mediate absorption of incident light by the dye. We separated out the role of plasmon resonances on absorption from emission. This was done using energy transfer in a donor–acceptor pair of dyes

Strong coupling between surface plasmon polaritons and emitters: a review

PublishedJournal Article"This is an author-created, un-copyedited version of an article published in Reports on Progress in Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/0034-4885/78/1/01390."In this review we look at the concepts and state-of-the-art concerning the strong coupling of surface plasmon-polariton modes to states associated with quantum emitters such as excitons in J-aggregates, dye molecules and quantum dots. We explore the phenomenon of strong coupling with reference to a number of examples involving electromagnetic fields and matter. We then provide a concise description of the relevant background physics of surface plasmon polaritons. An extensive overview of the historical background and a detailed discussion of more recent relevant experimental advances concerning strong coupling between surface plasmon polaritons and quantum emitters is then presented. Three conceptual frameworks are then discussed and compared in depth: classical, semi-classical and fully quantum mechanical; these theoretical frameworks will have relevance to strong coupling beyond that involving surface plasmon polaritons. We conclude our review with a perspective on the future of this rapidly emerging field, one we are sure will grow to encompass more intriguing physics and will develop in scope to be of relevance to other areas of science

Collective resonances in gold nanoparticle arrays

Baptiste Auguié and William L. Barnes, Physical Review Letters, Vol. 101, article 143902 (2008). Copyright © 2008 by the American Physical Society.We present experimental evidence of sharp spectral features in the optical response of 2D arrays of gold nanorods. A simple coupled dipole model is used to describe the main features of the observed spectral line shape. The resonance involves an interplay between the excitation of plasmons localized on the particles and diffraction resulting from the scattering by the periodic arrangement of these particles. We investigate this interplay by varying the particle size, aspect ratio, and interparticle spacing, and observe the effect on the position, width, and intensity of the sharp spectral feature

Plasmonic surface lattice resonances on arrays of different lattice symmetry

Arrays of metallic particles may exhibit optical collective excitations known as surface lattice resonances (SLRs). These SLRs occur near the diffraction edge of the array and can be sharper than the plasmon resonance associated with the isolated single particle response. We have fabricated and modeled arrays of silver nanoparticles of different geometries. We show that square, hexagonal, and honeycomb arrays show similar SLRs; no one geometry shows a clear advantage over the others in terms of resonance linewidth. We investigate the nature of the coupling between the particles by looking at rectangular arrays. Our results combine experiment and modeling based on a simple coupled-dipole model.Royal SocietyLeverhulme Trus

Manipulating type-I and type-II Dirac polaritons in cavity-embedded honeycomb metasurfaces

Pseudorelativistic Dirac quasiparticles have emerged in a plethora of artificial graphene systems that mimic the underlying honeycomb symmetry of graphene. However, it is notoriously difficult to manipulate their properties without modifying the lattice structure. Here we theoretically investigate polaritons supported by honeycomb metasurfaces and, despite the trivial nature of the resonant elements, we unveil rich Dirac physics stemming from a non-trivial winding in the light-matter interaction. The metasurfaces simultaneously exhibit two distinct species of massless Dirac polaritons, namely type-I and type-II. By modifying only the photonic environment via an enclosing cavity, one can manipulate the location of the type-II Dirac points, leading to qualitatively different polariton phases. This enables one to alter the fundamental properties of the emergent Dirac polaritons while preserving the lattice structure - a unique scenario which has no analog in real or artificial graphene systems. Exploiting the photonic environment will thus give rise to unexplored Dirac physics at the subwavelength scale

Efficient coupling of surface plasmon polaritons to radiation using a bi-grating

Copyright © 2001 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 79 (2001) and may be found at http://link.aip.org/link/?APPLAB/79/3035/1A nanostructured surface in the form of a bi-grating is shown to efficiently couple surface plasmon polaritons to free-space radiation in the visible part of the spectrum. Coupling was achieved for all propagation directions of the surface mode and the efficiency found to be independent of the propagation direction, taking a mean value of 60% for the structure examined. The consequences of the findings for emissive devices that make use of surface plasmons are discussed