Nanowire metamaterials play a pivotal role in a wide variety of applications including antennas research field and cancer detection in clinical practice. In the following we make a step forward by investigating properties of surface waves at the boundary of ellipsoidal nanowire metamaterial, specifically, we study effective properties of the ellipsoidal medium. The former could result in a possible application in clinical practice dealing with the cancer detection especially by having a deep insight into derived medium treatment approach due to the chosen model having similarities with the real biological systems containing cancer cells as the ellipsoidal inclusions. The future prospects could include translation of the obtained effective medium properties applying effective medium approximation models into cancer detection in clinical practice. The ultimate goal is to treat the investigated biological medium from the perspectives of the metamaterial theory.
Early detection of a tumor makes it more probable that the patient will, finally, recover. The current approach in diagnosis focuses on microbiological, immunological, and pathological aspects rather than on the “metamaterial geometry” of the diseases. The determination of the effective properties of the biological tissue samples and treating them as disordered media has become possible with the development of effective medium approximation techniques. The obtained effective permittivity values are affected by various factors, like the amount of different cell types in the sample. The identification of the cancer affected areas based on their effective medium properties was performed.
KEYWORDS: Metamaterials, Near field, Evanescence, Dielectrics, Hyperbolic metamaterials, Near field optics, Near field scanning optical microscopy, Design and modelling, Aluminum, Radio propagation
Conventional fiber-based metal coated aperture near-field probes offer a technologically easily reproducible and costfriendly option to achieve substantially good resolution in near-field imaging and lithography techniques, however the limiting mechanism behind the performance of these probes is the shape and the dimensions of the aperture. Hyperbolic metamaterials (HMM) have enabled the possibility to directly influence the propagation of highly-localized evanescent optical modes due to their extreme anisotropic properties. Implementation of such anisotropic metamaterial onto the tapered metal-coated probes offers a novel possibility to fabricate a probe capable of achieving the /7 resolution and better. This paper deals with a design and numerical characterization of plasmonic near-field probe consisting of tapered optical fiber coated with aluminium upon which a hyperbolic metamaterial is placed. The hyperbolic dispersive medium enables a directional propagation and interference of the highly-localized near-field waves.
Herein, we are making a step forward dealing with the novel theoretic and computational determination of the effective permittivity of the composite biological media. The presented methodology stands for as a perfect tool allowing to evaluate the permittivity tensor of the sample analytically with no needs of human intervention by performing an experimental analysis to measure the parameters of the sample. The distribution of the cancerous cells is taken into account. Doing so, we end up with the determination of the tensor components for random multi-phase composites. The former provides a fertile ground aiming to detect and treat cancer. It has been concluded that the increase of the concentration of the cancerous cells and their distribution in the sample makes a dramatic impact on the obtained numerical results.
Herein, we are making a step forward by treating cancerous tissues as the highly disordered anisotropic media. The classical Maxwell-Garnett technique is utilized. The former stands for as a perfect tool allowing to evaluate an effective medium of the sample analytically with no needs of human intervention by performing an experimental analysis to measure the parameters of the sample. It should be noted, that laboratory measurements of the effective properties are not needed in this case as well. In this relation, the presented technique allows for the creation of the phantom tissue models for the further usage in clinical applications.
Structural, optical, and electrical properties of ultrathin chromium films manufactured using magnetron sputtering were investigated. The films showed pure metallic chromium phase yet their refractive index and extinction coefficient result very different from previously reported in literature. Structural, electrical and optical properties of ultrathin chromium layers are discussed in detail. The obtained optical constants of ultrathin chromium films show a specific trend with the film thickness increase. Precise knowledge of optical constants of ultrathin chromium films is important for many electro-optical and optical applications.
Herein, we numerically investigate terahertz photoconductive antennas (PCAs) based on optimized plasmonic nanostructures and absorption enhancement in nanocylinders. Metallic nanostructures playing an important role in nanophotonic applications are a hot topic nowadays. Such applications are possible due to their capability to focus or intensify electromagnetic fields close to the metal by employing excitation approach of surface plasmon polaritons. Plasmonic behavior in the visible to near-infrared light spectrum is achievable due to the metallic nanostructures employment. Herein, we study the absorption enhancement of silver and transparent-conducting oxides (TCO) nanocylinders with different diameters by means of effective medium approximation. This study also reports on the stronger enhancement in the case of TCO nanocylinders. The results show that resonant absorption amplitude and wavelength are dramatically affected by the thickness of the nanostructure as well as by the distances between nanocylinders. The outputs reported here provide a fertile ground for precise control of the nanowire structures for sensing and other enhanced optical applications. Because of compact structure, simple fabrication and room temperature operation, PCAs provide THz wave generation and detection. Moreover, PCAs are widely used in time domain THz imaging and spectroscopy systems for generating pulsed THz radiation. It is worthwhile noting, that in case of TCO nanocylinders, absorption enhancement for NIR wavelengths, being relevant for present THz generation setup, reaches up to 5-fold leading to 25-fold increase in THz radiation.
Spoof plasmons are bound electromagnetic waves (EM) at frequencies outside the plasmonic range mimicking (“spoofing”) surface plasmons (SPs), which propagate on periodically corrugated metal surfaces. In recent years, electromagnetic waves propagating at an interface between a metal and dielectric have been of significant interest. Although most plasmonic research so far has focused on the near-infrared and optical ranges of the electromagnetic spectrum (where noble metals support highly confined surface waves), there exists an increasing interest in transferring SPs-based photonics to lower frequencies. However, in these spectral ranges, noble metals behave like perfect electric conductors, whose surface charges are able to screen any external EM excitation with extreme efficiency, preventing the formation of a tightly bound SP. It has been shown that the binding of EM fields to a metal surface can be increased by its corrugation. A surface of a metal perforated with a one-dimensional periodic array of rectangular grooves has already been considered. The question that remains open is the calculation of the effective permittivities for arbitrary grooves. The number of works describing the calculation of the effective dielectric constants for the grooved surfaces is limited. Here we have obtained an analytical dispersion relation of spoof plasmons on an arbitrary perforated surface of a real metal. We have derived analytical expressions for calculation of the permittivities of arbitrary grooves. Based on those results we have determined the minimum spot size for a triangular groove structure.
Optical waveguides have been a subject of an intensive theoretical research, resulting in applications in several fields, and stimulated research in integrated optics. Homogeneous dielectric waveguides and their properties are covered in detail in many articles and textbooks. However, in waveguides loaded with arbitrary inhomogeneous dielectrics, analytical solutions are possible only for a limited number of permittivity profiles in simple geometries. The analysis of longitudinally inhomogeneous waveguides has been already proposed, but the main drawback of this approach is that it requires cumbersome and time-consuming integration. We therefore suggest to take this a step further by applying our new original analytical approach that does not require integration. The aim of this work is to establish a different method that is generally applicable to any vectorial time-dependent, anisotropic, non-linear, inhomogeneous, dissipative and dispersive media to analyze the field distribution of inhomogeneous 1-D and 2-D waveguides with symmetric and asymmetric permittivity profiles. Our initial consideration of slab problems with arbitrary profiles by means of analytical method shows a great deal of potential for use in applications in fields such as physics, and engineering.
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