“Unlocking” the Ground: Increasing the Detectability of Buried Objects by Depositing Passive Superstrates

One of the main problems when trying to detect the position and other characteristics of a small inclusion into lossy earth via external measurements is the inclusion’s poor scattering response due to attenuation. Hence, increasing the scattered power generated by the inclusion by using not an active but a passive material is of great interest. To this direction, we examine, in this work, a procedure of “unlocking” the ground by depositing a thin passive layer of conventional material atop of it. The first step is to significantly enhance the transmission into a lossy half space, in the absence of the inclusion, by covering it with a passive slab. The redistribution of the fields into the slab and the infinite half space, due to the interplay of waves between the interfaces, makes possible to determine the thickness and permittivity of an optimal layer. The full boundary value problem (including the inclusion and the deposited superstrate) is solved semi-analytically via integral equations techniques. Then, the scattered power of the buried inclusion is compared to the corresponding quantity when no additional layer is present. We report substantial improvement in the detectability of the inclusion for several types of ground and burying depths by using conventional realizable passive materials. Implementation aspects in potential applications as well as possible future generalizations are also discussed. The developed technique may constitute an effective “configuration (structural) preprocessing” which may be used as a first step in the analysis of related problems before the application of an inverse scattering algorithm concerning the efficient processing of the scattering dat

Optical PT-Symmetric Counterparts of Ordinary Metals

How one can fabricate the Parity-Time (PT) symmetric siblings of commonly used metals in the visible? This work tries to give an answer to that question by providing the features of the active media which conjugately pair the complex permittivities of ordinary metals (Copper, Aluminum, Silver, Gold, Platinum) at the optical frequencies. The frequency response model of quantum dots (QDs) is used to evaluate the effective permittivity of the active material; their characteristics which give a PT-symmetric counterpart for the considered metal are deduced through a multi-step optimization process. The required resonance frequencies, loss factors and degrees of population inversion for the QDs are provided for various frequencies and metals. The response of the metals when they are PT-symmetrically coupled with the provided mixtures is demonstrated in specific photonic configurations and interesting properties with certain applicability potential are reveale

“Unlocking” the Ground: Increasing the Detectability of Buried Objects by Depositing Passive Superstrates

One of the main problems when trying to detect the position and other characteristics of a small inclusion into lossy earth via external measurements is the inclusion’s poor scattering response due to attenuation. Hence, increasing the scattered power generated by the inclusion by using not an active but a passive material is of great interest. To this direction, we examine, in this work, a procedure of “unlocking” the ground by depositing a thin passive layer of conventional material atop of it. The first step is to significantly enhance the transmission into a lossy half space, in the absence of the inclusion, by covering it with a passive slab. The redistribution of the fields into the slab and the infinite half space, due to the interplay of waves between the interfaces, makes possible to determine the thickness and permittivity of an optimal layer. The full boundary value problem (including the inclusion and the deposited superstrate) is solved semi-analytically via integral equations techniques. Then, the scattered power of the buried inclusion is compared to the corresponding quantity when no additional layer is present. We report substantial improvement in the detectability of the inclusion for several types of ground and burying depths by using conventional realizable passive materials. Implementation aspects in potential applications as well as possible future generalizations are also discussed. The developed technique may constitute an effective “configuration (structural) preprocessing” which may be used as a first step in the analysis of related problems before the application of an inverse scattering algorithm concerning the efficient processing of the scattering dat

Judiciously distributing laser emitters to shape the desired far field patterns

The far-field pattern of a simple one-dimensional laser array of emitters radiating into free space is considered. In the path of investigating the inverse problem for their near fields leading to a target beam form, surprisingly we found that the result is successful when the matrix of the corresponding linear system is not well-scaled. The essence of our numerical observations is captured by an elegant inequality defining the functional range of the optical distance between two neighboring emitters. Our finding can restrict substantially the parametric space of integrated photonic systems and simplify significantly the subsequent optimizations

Optimized Operation of Photonic Devices With Use of Ordinary Bulk Materials

Structural boundaries, materials and feeding sources are the three fundamental segments defining photonic devices. Since excitation is usually dictated by the application and there are infinite ways to select the spatial configuration of the component, an optimization with respect to the used media is both doable and useful. We provide several combinations of elements and compounds making high-performing electromagnetic devices in terms of absorption, scattering and unusual refraction with simple structures like bilayers, two- and three- dimensional core-shell particles or binary metasurfaces. Such large sets of potential candidates for the employed media can be deployed by experimentalists after applying a secondary sweep by imposing additional constraints concerning ease of fabrication

Maximal Interaction of Electromagnetic Radiation with Corona-Virions

Absorption and scattering of the impinging electromagnetic waves are the two fundamental operations describing the energy exchange of any, organic or inorganic, particle with its environment. In the case of virion cells, substantial extinction power, counting both absorbing and scattering effects, is a prerequisite for performing a variety of coupling actions against the viral particles and, thus, a highly sought-after feature. By considering realistic dispersion for the dielectric permittivity of proteins and a core-shell modeling allowing for rigorous formulation via Mie theory, we report optical extinction resonances for corona-virions at mid-infrared range that are not significantly perturbed by changes in the objects size or the background host. Our findings indicate the optimal regime for interaction of photonic radiation with viral particles and may assist towards the development of equipment for thermal damage, disintegration or neutralization of coronavirus cells.Comment: 8 pages, 7 figures. Submitted to: APL Photonics, special topic on "Coronavirus and Photonics

Electromagnetic cloaking of cylindrical objects by multilayer or uniform dielectric claddings

We show that dielectric or even perfectly conducting cylinders can be cloaked by a uniform or a layered dielectric cladding, without the need of any exotic or magnetic material parameters. In particular, we start by presenting a simple analytical concept that can accurately describe the cloaking effect obtained with conical silver plates in the visible spectrum. The modeled structure has been originally presented in [S. A. Tretyakov, P. Alitalo, O. Luukkonen, C. R. Simovski, Phys. Rev. Lett., vol. 103, p. 103905, 2009], where its operation as a cloak in the optical frequencies was studied only numerically. We model rigorously this configuration as a multi-layer dielectric cover surrounding the cloaked object, with excellent agreement to the simulation results of the actual device. The concept of using uniform or multilayer dielectric covers, with relative permittivities larger than unity, is then successfully extended to cloaking of impenetrable objects such as conducting cylinders.Comment: 14 pages, 9 figure

Highly selective transmission and absorption from metasurfaces of periodically corrugated cylindrical particles

Gratings of infinite wires make, perhaps, the simplest class of metasurfaces, which, however, are utilized for a variety of different objectives in wave manipulation. Importantly, due to their analytical solvability, they can be fully optimized in a fast and direct way. In this study, a lattice of periodically corrugated cylindrical particles under oblique plane-wave excitation is considered and treated rigorously. Several cases of particle radii, distances between two consecutive cylinders, and angles of illumination are examined; as a result, very high selectivity of the metasurface response in terms of line-of-sight transmission and absorption is reported. That abrupt change in the device output becomes even more dramatic in the parametric vicinity of the emergence of new refractive orders, which makes the proposed metasurface exceptionally fitting for switching, filtering, and sensing application