Non-minimal monopoles of the Dirac type as realization of the censorship conjecture

We discuss a class of exact solutions of a three-parameter non-minimally extended Einstein-Maxwell model, which are attributed to non-minimal magnetic monopoles of the Dirac type. We focus on the investigation of the gravitational field of Dirac monopoles for those models, for which the singularity at the central point is hidden inside of an event horizon independently on the mass and charge of the object. We obtained the relationships between the non-minimal coupling constants, for which this requirement is satisfied. As explicit examples, we consider in detail two one-parameter models: first, non-minimally extended Reissner-Nordstr\"om model (for the magnetically charged monopole), second, the Drummond-Hathrell model.Comment: 9 pages; one reference added, accepted to Phys. Rev.

Structural second-order nonlinearity in metamaterials

Nonlinear processes are at the core of many optical technologies including lasers, information processing, sensing, and security, and require optimised materials suitable for nanoscale integration. Here we demonstrate the emergence of a strong bulk second-order nonlinear response in a composite plasmonic nanorod material comprised of centrosymmetric materials. The metamaterial provides equally strong generation of the p-polarized second harmonic light in response to both s- and p-polarized excitation. We develop an effective-medium description of the underlying physics, compare its predictions to the experimental results and analyze the limits of its applicability. We show that while the effective medium theory adequately describes the nonlinear polarization, the process of emission of second harmonic light cannot be described in the same framework. The work provides an understanding of the emergent nonlinear optical response in composites and opens a doorway to new nonlinear optical platform designs for integrated nonlinear photonics

Controlling Boron Diffusion during Rapid Thermal Annealing with CoImplantation by Amphoteric Impurity Atoms

A model for simulating the rapid thermal annealing of silicon structures implanted with boron and carbon is developed. The model provides a fair approximation of the process of boron diffusion in silicon, allowing for such effects as the electric field, the impact of the implanted carbon, and the clustering of boron. The migration process of interstitials is described according to their drift in the field of internal elastic stress

Nonminimal isotropic cosmological model with Yang-Mills and Higgs fields

We establish a nonminimal Einstein-Yang-Mills-Higgs model, which contains six coupling parameters. First three parameters relate to the nonminimal coupling of non-Abelian gauge field and gravity field, two parameters describe the so-called derivative nonminimal coupling of scalar multiplet with gravity field, and the sixth parameter introduces the standard coupling of scalar field with Ricci scalar. The formulated six-parameter nonminimal Einstein-Yang-Mills-Higgs model is applied to cosmology. We show that there exists a unique exact cosmological solution of the de Sitter type for a special choice of the coupling parameters. The nonminimally extended Yang-Mills and Higgs equations are satisfied for arbitrary gauge and scalar fields, when the coupling parameters are specifically related to the curvature constant of the isotropic spacetime. Basing on this special exact solution we discuss the problem of a hidden anisotropy of the Yang-Mills field, and give an explicit example, when the nonminimal coupling effectively screens the anisotropy induced by the Yang-Mills field and thus restores the isotropy of the model.Comment: 15 pages, revised version accepted to Int. J. Mod. Phys. D, typos correcte

Single-photon tunneling

Strong evidence of a single-photon tunneling effect, a direct analog of single-electron tunneling, has been obtained in the measurements of light tunneling through individual subwavelength pinholes in a thick gold film covered with a layer of polydiacetylene. The transmission of some pinholes reached saturation because of the optical nonlinearity of polydiacetylene at a very low light intensity of a few thousands photons per second. This result is explained theoretically in terms of "photon blockade", similar to the Coulomb blockade phenomenon observed in single-electron tunneling experiments. The single-photon tunneling effect may find many applications in the emerging fields of quantum communication and information processing.Comment: 4 pages, 4figure

Temperature stability of thin film refractory plasmonic materials

Materials such as W, TiN, and SrRuO3 (SRO) have been suggested as promising alternatives to Au and Ag in plasmonic applications owing to their stability at high operational temperatures. However, investigation of the reproducibility of the optical properties after thermal cycling between room and elevated temperatures is so far lacking. Here, thin films of W, Mo, Ti, TiN, TiON, Ag, Au, SrRuO3 and SrNbO3 are investigated to assess their viability for robust refractory plasmonic applications. These results are further compared to the performance of SrMoO3 reported in literature. Films ranging in thickness from 50 to 105 nm are deposited on MgO, SrTiO3 and Si substrates by e-beam evaporation, RF magnetron sputtering and pulsed laser deposition, prior to characterisation by means of AFM, XRD, spectroscopic ellipsometry, and DC resistivity. Measurements are conducted before and after annealing in air at temperatures ranging from 300 to 1000° C for one hour, to establish the maximum cycling temperature and potential longevity at elevated temperatures for each material. It is found that SrRuO3 retains metallic behaviour after annealing at 800° C, while SrNbO3 undergoes a phase transition resulting in a loss of metallic behaviour after annealing at 400° C. Importantly, the optical properties of TiN and TiON are degraded as a result of oxidation and show a loss of metallic behaviour after annealing at 500° C, while the same is not observed in Au until annealing at 600° C. Nevertheless, both TiN and TiON may be better suited than Au or SRO for high temperature applications operating under vacuum conditions

Discrete structure of ultrathin dielectric films and their surface optical properties

The boundary problem of linear classical optics about the interaction of electromagnetic radiation with a thin dielectric film has been solved under explicit consideration of its discrete structure. The main attention has been paid to the investigation of the near-zone optical response of dielectrics. The laws of reflection and refraction for discrete structures in the case of a regular atomic distribution are studied and the structure of evanescent harmonics induced by an external plane wave near the surface is investigated in details. It is shown by means of analytical and numerical calculations that due to the existence of the evanescent harmonics the laws of reflection and refraction at the distances from the surface less than two interatomic distances are principally different from the Fresnel laws. From the practical point of view the results of this work might be useful for the near-field optical microscopy of ultrahigh resolution.Comment: 25 pages, 16 figures, LaTeX2.09, to be published in Phys.Rev.

ЧИСЛЕННОЕ ИССЛЕДОВАНИЕ СТРУКТУРЫ МАГНИТНОГО ПОЛЯ В ЦИЛИНДРИЧЕСКОМ ПЛЕНОЧНОМ ЭКРАНЕ

A numerical method for solving the boundary value problem for a nonlinear magnetostatic equation describing the external magnetostatic field penetration through the cylindrical film coating is developed. A mathematical model of the shielding problem based on the use of the boundary conditions of the third kind on the film surface is studied. The nonlinear dependence of the film magnetic permeability on magnetic field conforms with experimental data. The distribution of the magnetic field strength in the film layer and the magnetic permeability of the film material depending on the magnitude of the external magnetic field strength are investigated numerically.Разрабатывается численный метод решения краевой задачи для нелинейного уравнения магнитостатики, описывающей проникновение постоянного внешнего магнитного поля через цилиндрическую пленочную оболочку. Изучается математическая модель задачи экранирования, основанная на использовании граничных условий третьего рода на поверхности пленки. Нелинейная зависимость магнитной проницаемости пленки от напряженности магнитного поля согласовывается с экспериментальными данными. Численно исследуется распределение напряженности магнитного поля в слое пленки и магнитной проницаемости материала пленки в зависимости от величины напряженности внешнего магнитного поля

Circular Dichroism Enhancement in Plasmonic Nanorod Metamaterials

Optical activity is a fundamental phenomenon originating from the chiral nature of crystals and molecules. While intrinsic chiroptical responses of ordinary chiral materials to circularly polarized light are relatively weak, they can be enhanced by specially tailored nanostructures. Here, nanorod metamaterials, comprising a dense array of vertically aligned gold nanorods, is shown to provide significant enhancement of the circular dichroism response of an embedded material. A nanorod composite, acting as an artificial uniaxial crystal, is filled with chiral mercury sulfide nanocrystals embedded in a transparent polymer. The nanorod based metamaterial, being inherently achiral, enables optical activity enhancement or suppression. Unique properties of inherently achiral structures to tailor optical activities pave a way for flexible characterization of optical activity of molecules and nanocrystal-based compounds