Samel Arslanagic

Active coated nano-particle excited by an arbitrarily located electric Hertzian dipole?resonance and transparency effects

The present work investigates the optical properties of active coated spherical nano-particles excited by an arbitrarily located electric Hertzian dipole. The nano-particles are made of specific dielectric and plasmonic materials. The spatial near-field distribution as well as the normalized radiation resistance is examined. Both enhanced as well as reduced radiation effects are demonstrated. In particular, it is shown that specific active coated nano-particles can be designed to be resonant, leading to much larger values of the normalized radiation resistance than is the case with the corresponding passive coated nano-particles, thereby overcoming the intrinsic losses present in the plasmonic materials. Moreover, it is shown that other active coated nano-particle designs can significantly reduce the normalized radiation resistance; thus both the resonant as well as non-radiating/transparent states of the active coated nano-particle are identified. Implications of both the resonant and non-radiating states on the previously proposed localized sensors based on the active coated nano-particle will also be considered here.

Electric-line-source illumination of a circular cylinder of lossless double-negative material: an investigation of near field, directivity, and radiation resistance

his work investigates the properties of an antenna-like configuration with an electric line source radiating in the presence of a double-negative circular cylinder. First, the analytical eigenfunction-series solution is derived. Second, this solution is employed in numerical calculations to study the properties of the near field, inside as well as outside the cylinder, and the far-field. Third, the variations of these fields are examined, as well as the radiation resistance and radiation pattern, as functions of the geometrical and electromagnetic parameters of the configuration. It is demonstrated that the scattering properties of the double-negative cylinder are vastly different from those of the corresponding double-positive cylinder. In particular, the focusing effect inside the cylinder and the angular variation of the directivity exhibit distinct characteristics

Impact of the Excitation Source and Plasmonic Material on Cylindrical Active Coated Nano-Particles

Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation characteristics, in the presence of an electric or a magnetic line source. A constant frequency canonical gain model is used to account for the gain introduced in the dielectric part of the nano-particle, whereas three different plasmonic materials (silver, gold, and copper) are employed and compared for the nano-shell layers.

Influence of active nano particle size and material composition on multiple quantum emitter enhancements: Their enhancement and jamming effects

In the 150 years that scientists and engineers have used Maxwells equations to describe electromagnetic phenomena, canonical scattering and radiating problems have played a very important role, providing explanations of and insights into their underlying physics. With the same intent, a variety of active coated nano-particles are examined here theoretically with regard to their ability to effectively enhance or jam the responses of quantum emitters, e.g., fluorescing molecules, and nano- antennas to an observer located in their far-field regions. The investigated spherical particles consist of a gain-impregnated silica nano-core covered with a nano-shell of a specific plasmonic material. Attention is devoted to the influence of the over-all size of these particles and their material composition on the obtained levels of active enhancement or jamming. Silver, gold and copper are employed as their nano- shells. The over-all diameters of the investigated coated nano-particles are taken to be 20 nm, 40 nm, and 60 nm, while maintaining the same ratio of the core radius and shell thickness. It is shown that the jamming levels, particularly when several emitters are present, are significantly larger for particles of larger sizes. These configurations are also shown to lead to the largest enhancement levels of the surrounding quantum emitters. Furthermore, for a fixed particle size and for a gain constant that produces the largest enhancement peak at optical wavelengths, it is demonstrated that these larger levels are most notable when the nano-shell is gold.

Near-field distribution, directivity and differential scattering cross section for a line source-excited metamaterial-coated electrically small cylinder

An antenna configuration consisting of an arbitrarily located electric line source radiating in the presence of concentric metamaterial cylinders is examined. In particular, the near field, the directivity, and the differential scattering cross section are investigated for specific metamaterial structures, and these results are compared to those for the corresponding structures based on double-positive materials. It is shown that specific electrically small metamaterial structures possess radiation and scattering features that surpass those of the corresponding double-positive material structures.

Coated nano-particle jamming of quantum emitters

Spherical active coated nano-particles are examined analytically and numerically in the presence of one, two or four quantum emitters (electric Hertzian dipoles). The ability of the coated nano-particle to effectively cloak the emitters to a far-field observer is reported. This offers an interesting route towards the jamming of quantum emitters/nano-antennas, for instance, in biological fluorescence assays.

Sub-Wavelength Resonances in Metamaterial-Based Multi-Cylinder Configurations

Sub-wavelength resonances known to exist in isolated metamaterial-based structures of circular cylindrical shape are investigated with the purpose of determining whether the individual resonances are retained when several of such resonant structures are grouped to form a new structure. To this end, structures consisting of 1, 2 and 4 sets of metamaterial-based concentric cylinders excited by an electric line current are analyzed numerically. It is demonstrated that these structures recover the resonances of the individual structures even when the cylinders are closely spaced and the new structure is thus electrically small. The investigation is conducted through a detailed analysis of the electric near-field distribution as well as the radiation resistance in those cases where the individual structures are made of simple dielectric materials in conjunction with simple, but lossy and dispersive, metamaterials.

A numerical investigation of sub-wavelength resonances in polygonal metamaterial cylinders

The sub-wavelength resonances, known to exist in metamaterial radiators and scatterers of circular cylindrical shape, are investigated with the aim of determining if these resonances also exist for polygonal cylinders and, if so, how they are affected by the shape of the polygon. To this end, a set of polygonal cylinders excited by a nearby electric line current is analyzed numerically and it is shown, through detailed analysis of the near-field distribution and radiation resistance, that these polygonal cylinders do indeed support sub-wavelength resonances similar to those of the circular cylinders. The dispersion and loss, inevitably present in realistic metamaterials, are modeled by the Drude and Lorentz dispersion models to study the bandwidth properties of the resonances.

Far-Field Properties of a Line Source-Excited Electrically Small Quadrupolar Metamaterial Cylindrical Shell

An antenna configuration that consists of an arbitrarily located electric line source that radiates in the presence of concentric metamaterial cylinders is examined. With the emphasis on the so-called quadrupolar structure, it is shown that such electrically small configurations may offer significant enhancements of the radiated power. Furthermore, the possibility of controlling the pattern by properly locating the electric line source with respect to the structure, thereby offering a means of obtaining electrically small metamaterial-based directive antennas, is also demonstrated.

Control of exceptional points in photonic crystal slabs

Various ways of controlling the extent of the ring of exceptional points in photonic crystal slabs are investigated. The extent of the ring in photonic crystal slabs is found to vary with the thickness of the slab. This enables recovery of Dirac cones in open, non-Hermitian systems, such as a photonic crystal slab. In this case, all three bands exhibit a bound state in the continuum in close proximity of the Γ point. These results may lead to new designs of small photonic-crystal-based lasers exhibiting high-quality factors.