86 research outputs found
Spatial coherence and stability in a disordered organic polariton condensate
Although only a handful of organic materials have shown polariton
condensation, their study is rapidly becoming more accessible. The spontaneous
appearance of long-range spatial coherence is often recognized as a defining
feature of such condensates. In this work, we study the emergence of spatial
coherence in an organic microcavity and demonstrate a number of unique features
stemming from the peculiarities of this material set. Despite its disordered
nature, we find that correlations extend over the entire spot size and we
measure values of nearly unity at short distances and of 50%
for points separated by nearly 10 m. We show that for large spots, strong
shot to shot fluctuations emerge as varying phase gradients and defects,
including the spontaneous formation of vortices. These are consistent with the
presence of modulation instabilities. Furthermore, we find that measurements
with flat-top spots are significantly influenced by disorder and can, in some
cases, lead to the formation of mutually incoherent localized condensates.Comment: Revised versio
Observation of quantum interference in the plasmonic Hong-Ou-Mandel effect
We report direct evidence of the bosonic nature of surface plasmon polaritons
(SPPs) in a scattering-based beamsplitter. A parametric down-conversion source
is used to produce two indistinguishable photons, each of which is converted
into a SPP on a metal-stripe waveguide and then made to interact through a
semi-transparent Bragg mirror. In this plasmonic analog of the Hong-Ou-Mandel
experiment, we measure a coincidence dip with a visibility of 72%, a key
signature that SPPs are bosons and that quantum interference is clearly
involved.Comment: 5 pages, 3 figure
Microscopic theory of polariton lasing via vibronically assisted scattering
Polariton lasing has recently been observed in strongly coupled crystalline
anthracene microcavities. A simple model is developed describing the onset of
the non-linear threshold based on a master equation including the relevant
relaxation processes and employing realistic material parameters. The mechanism
governing the build-up of the polariton population - namely bosonic stimulated
scattering from the exciton reservoir via a vibronically assisted process - is
characterized and its efficiency calculated on the basis of a microscopic
theory. The role of polariton-polariton bimolecular quenching is identified and
temperature dependent effects are discussed.Comment: 7 pages main text plus 3 appendices. 10 figure
Strong light-matter coupling in two-dimensional atomic crystals
Two dimensional (2D) atomic crystals of graphene, and transition metal
dichalcogenides have emerged as a class of materials that show strong
light-matter interaction. This interaction can be further controlled by
embedding such materials into optical microcavities. When the interaction is
engineered to be stronger than the dissipation of light and matter entities,
one approaches the strong coupling regime resulting in the formation of
half-light half-matter bosonic quasiparticles called microcavity polaritons.
Here we report the evidence of strong light-matter coupling and formation of
microcavity polaritons in a two dimensional atomic crystal of molybdenum
disulphide (MoS2) embedded inside a dielectric microcavity at room temperature.
A Rabi splitting of 46 meV and highly directional emission is observed from the
MoS2 microcavity owing to the coupling between the 2D excitons and the cavity
photons. Realizing strong coupling effects at room temperature in a disorder
free potential landscape is central to the development of practical polaritonic
circuits and switches.Comment: 25 pages, 7 figure
Quantum Statistics of Surface Plasmon Polaritons in Metallic Stripe Waveguides
Single surface plasmon polaritons are excited using photons generated via
spontaneous parametric down-conversion. The mean excitation rates, intensity
correlations and Fock state populations are studied. The observed dependence of
the second order coherence in our experiment is consistent with a linear
uncorrelated Markovian environment in the quantum regime. Our results provide
important information about the effect of loss for assessing the potential of
plasmonic waveguides for future nanophotonic circuitry in the quantum regime.Comment: 21 pages, 6 figures, published in Nano Letters, publication date
(web): March 27 (2012
Near-field interactions between metal nanoparticle surface plasmons and molecular excitons in thin-films: part I: absorption
In this and the following paper (parts I and II, respectively), we systematically study the interactions between surface plasmons of metal nanoparticles (NPs) with excitons in thin-films of organic media. In an effort to exclusively probe near-field interactions, we utilize spherical Ag NPs in a size-regime where far-field light scattering is negligibly small compared to absorption. In part I, we discuss the effect of the presence of these Ag NPs on the absorption of the embedding medium by means of experiment, numerical simulations, and analytical calculations, all shown to be in good agreement. We observe absorption enhancement in the embedding medium due to the Ag NPs with a strong dependence on the medium permittivity, the spectral position relative to the surface plasmon resonance frequency, and the thickness of the organic layer. By introducing a low index spacer layer between the NPs and the organic medium, this absorption enhancement is experimentally confirmed to be a near field effect In part II, we probe the impact of the Ag NPs on the emission of organic molecules by time-resolved and steady-state photoluminescence measurements
Advances in small lasers
M.T.H was supported by an Australian Research council Future Fellowship research grant for this work. M.C.G. is grateful to the Scottish Funding Council (via SUPA) for financial support.Small lasers have dimensions or modes sizes close to or smaller than the wavelength of emitted light. In recent years there has been significant progress towards reducing the size and improving the characteristics of these devices. This work has been led primarily by the innovative use of new materials and cavity designs. This Review summarizes some of the latest developments, particularly in metallic and plasmonic lasers, improvements in small dielectric lasers, and the emerging area of small bio-compatible or bio-derived lasers. We examine the different approaches employed to reduce size and how they result in significant differences in the final device, particularly between metal- and dielectric-cavity lasers. We also present potential applications for the various forms of small lasers, and indicate where further developments are required.PostprintPeer reviewe
Polaritonic molecular clock for all-optical ultrafast imaging of wavepacket dynamics without probe pulses
Conventional approaches to probing ultrafast molecular dynamics rely on the use of synchronized laser pulses with a well-defined time delay. Typically, a pump pulse excites a molecular wavepacket. A subsequent probe pulse can then dissociate or ionize the molecule, and measurement of the molecular fragments provides information about where the wavepacket was for each time delay. Here, we propose to exploit the ultrafast nuclear-position-dependent emission obtained due to large lightâmatter coupling in plasmonic nanocavities to image wavepacket dynamics using only a single pump pulse. We show that the time-resolved emission from the cavity provides information about when the wavepacket passes a given region in nuclear configuration space. This approach can image both cavity-modified dynamics on polaritonic (hybrid lightâmatter) potentials in the strong lightâmatter coupling regime and bare-molecule dynamics in the intermediate coupling regime of large Purcell enhancements, and provides a route towards ultrafast molecular spectroscopy with plasmonic nanocavitiesThis work has been funded by the European Research Council grant ERC-2016-STG-714870 and the Spanish Ministry for Science, Innovation, and UniversitiesâAEI grants RTI2018-099737-B-I00, PCI2018-093145 (through the QuantERA program of the European Commission), and CEX2018-000805-M (through the MarĂa de Maeztu program for Units of Excellence in R&D
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