We present an analytic theory for the optical properties of ellipsoidal plasmonic particles covered by anisotropic molecular layers. The theory is applied to the case of a prolate spheroid covered by chromophores oriented parallel and perpendicular to the metal surface. For the case that the molecular layer resonance frequency is close to being degenerate with one of the particle plasmon resonances strong hybridization between the two resonances occur. Approximate analytic expressions for the hybridized resonance frequencies, their extinction cross section peak heights and widths are derived. The strength of the molecular - plasmon interaction is found to be strongly dependent on molecular orientation and suggest that this sensitivity could be the basis for novel nanoparticle based bio/chemo-sensing applications.
Metal nanoparticles are the most frequently used nanostructures in plasmonics. However, besides nanoparticles, metal nanowires feature several advantages for applications. Their elongation offers a larger interaction volume, their resonances can reach higher quality factors, and their mode structure provides better coupling into integrated hybrid dielectric-plasmonic circuits. It is crucial though, to control the distance of the wire to a supporting substrate, to another metal layer or to active materials with sub-nanometer precision. A dielectric coating can be utilized for distance control, …
Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflection properties of all-dielectric and plasmonic nanoparticle coatings based on silver and crystalline silicon. Our results of numerical simulations for periodic arrays of spherical nanoparticles on top of amorphous silicon show that both silicon an…
Plasmonic nanoantennas, the properties of which are essentially determined by their resonance modes, are of interest both fundamentally and for various applications. Antennas with various shapes, geometries and compositions have been demonstrated, each possessing unique properties and potential applications. Here, we propose the use of a sidewall coating as an additional degree of freedom to manipulate plasmonic gap cavity modes in strongly coupled metallic nanodisks. It is demonstrated that for a dielectric middle layer with a thickness of a few tens of nanometers and a sidewall plasmonic coa…
The evidence of strong coupling between plasmons and molecular excitons for plasmonic nanoparticle (NP) dimers exhibiting ultra-sensitive surface enhanced resonant Raman scattering is the observation of anti-crossing in the coupled resonance. However, it is not easy to experimentally tune plasmon resonance of such dimers for the observation. In this work, we theoretically investigate the anti-crossing properties of the dimers coated by the thin dye films with thicknesses greater than 0.1 nm and gap distances larger than 1.2 nm according to the principles of classical electromagnetism. The plas…
Nanoparticle (NP) arrays of noble metals strongly absorb light in the visible to infrared wavelengths through resonant interactions between the incident electromagnetic field and the metal's free electron plasma. Such plasmonic interfaces enhance light absorption and photocurrent in solar cells. We report a cost effective and scalable room temperature/pressure spin-coating route to fabricate broadband plasmonic interfaces consisting of silver NPs. The NP interface yields photocurrent enhancement (PE) in thin film silicon devices by up to 200% which is significantly greater than previously repo…
Using the finite element method we investigate plasmon-mediated transmission in a periodically modulated metal-insulator-metal (MIM) grating. We compute the eigenmodes of a silver-silica-silver conformal coating atop an array of close-packed silica rods, and correlate them with extinction and transmission characteristics of the structure. We observe efficient coupling of impinging plane-waves to gap plasmon modes, allowing control of both bandwidth and intensity of the transmitted radiation.
We propose a composite layered structure for tunable, low-loss plasmon resonances, which con- sists of a noble-metal thin film coated in graphene and supported on a hexagonal boron nitride (hBN) substrate. We calculate electron energy loss spectra (EELS) for these structures, and nu- merically demonstrate that bulk plasmon losses in noble-metal films can be significantly reduced, and surface coupling enhanced, through the addition of a graphene coating and the wide-bandgap hBN substrate. Silver films with a trilayer graphene coating and hBN substrate demonstrated sur- face plasmon-dominant spe…
This review describes hybrid photonic-plasmonic structures based on periodic structures that have metallic coatings or inserts which make use of the Tamm plasmon for sensing applications. The term Tamm plasmon refers a particular resonance resulting from the enhancement of a surface plasmon resonance absorption via coupling to a wavelength-matching photonic bandgap provided by a photonic crystal. Tamm plasmon-based devices come in an ample variety of material and geometric combinations, each designed to perform a specific kind of measurement. While the physical effect is quite well documented …
The UV enhancement of Al-coated ZnO single crystals with a wide range of carrier densities is systematically studied using depth-resolved cathodoluminescence (CL) and photoluminescence (PL) as well as valence band X-ray photoemission spectroscopy (VB-XPS). AN up to 17-fold enhanced PL UV emission for Al-coated ZnO with the highest carrier density (2 x 10^17 cm^-3) was measured, which falls to a 12-fold increase for the lowest carrier density (3 x 10^13 cm^-3). Depth-resolved CL measurements confirm that the enhancement is strongest near the metal coating-ZnO interface consistent with an increa…
The realization and control of polaritons is of paramount importance in the prospect of novel photonic devices. Here, we investigate the emergence of plasmon-exciton polaritons in hybrid structures consisting of a two-dimensional (2D) transition metal dichalcogenide (TMDC) deposited onto a metal substrate or coating a metallic thin-film. We determine the polaritonic spectrum and show that, in the former case, the addition of a top dielectric layer, and, in the latter, the thickness of the metal film,can be used to tune and promote plasmon-exciton interactions well within the strong coupling re…
Sub-nanometer 3D morphometric precision of polarisation-resolved wide-field optical extinction microscopy determines the roundness of individual gold nanospheres
Tailoring and enhancing the interaction between light and matter is of great importance for both fundamental researches and future photonic and optoelectronic applications. Due to their high exciton oscillator strength and large exciton binding energy, two-dimensional atomic semiconducting transition metal dichalcogenides have recently emerged as an excellent platform for the strong photon-exciton interaction by integrating with optically resonant cavities. Here, we propose an all-semiconductor system composed of individual silicon nanospheres and monolayer WS2 and investigate the resonance co…
Metal nanoparticle (NP) surface coatings are known to significantly enhance the ultra-violet luminescence intensity of ZnO. Although there is general agreement that resonantly excited Localized Surface Plasmons (LSPs) in metal NPs can directly couple to excitons in the semiconductor increasing their spontaneous emission rate, the exact mechanisms involved in this phenomenon are currently not fully understood. In this work, LSP-exciton coupling in a ZnO single crystal and ZnO nanorods coated with a 2 nm Al layer has been investigated using correlative photoluminescence and depth-resolved cathod…
