Electromagnetic Absorption of Gaussian Beams by a Grounded Layered Structure

A layered structure of magnetodielectric slabs, backed with a perfectly conducting plane, is illuminated by a Gaussian beam. The permittivities and permeabilities of each layer are selected so that the incident field penetrates smoothly into the subsequent layers and sustains gradually greater losses when reaching the internal ones. The performance of the device as an absorber is estimated through a newly defined indicator and it has been found that the absorbing capacity of the structure could be very high. This qualitative factor is robust and efficient when identifying which of the considered parameters are critical or insignificant as far as the performance of the layered configuration is concerned

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

On-Site Wireless Power Generation

Conventional wireless power transfer systems consist of a microwave power generator and a microwave power receiver separated by some distance. To realize efficient power transfer, the system is typically brought to resonance, and the coupled-antenna mode is optimized to reduce radiation into the surrounding space. In this scheme, any modification of the receiver position or of its electromagnetic properties results in the necessity of dynamically tuning the whole system to restore the resonant matching condition. It implies poor robustness to the receiver location and load impedance, as well as additional energy consumption in the control network. In this study, we introduce a new paradigm for wireless power delivery based on which the whole system, including transmitter and receiver and the space in between, forms a unified microwave power generator. In our proposed scenario the load itself becomes part of the generator. Microwave oscillations are created directly at the receiver location, eliminating the need for dynamical tuning of the system within the range of the self-oscillation regime. The proposed concept has relevant connections with the recent interest in parity-time symmetric systems, in which balanced loss and gain distributions enable unusual electromagnetic responses.Comment: 10 pages, 13 figure

Conjugately-Matched Uniaxial Metamaterials Make Extremely Efficient Absorbers, Emitters, and Reflectors

The speed with which electromagnetic energy can be wirelessly transferred from a source to the user is a crucial parameter for performance of a large number of electronic and photonic devices. In this presentation we determine the constituent parameters of a medium which supports theoretically infinite energy concentration close to a medium sample surface; such a material combines properties of Perfectly Matched Layers (PML) and Double-Negative (DNG) media. It realizes conjugate matching with free space for every possible mode including, most importantly, all evanescent modes. We show that extremely high-amplitude resonating fields in the vicinity of a conjugately matched body can create large far-field radiation with the use of randomly placed particles which play the role of emission “vessels”

Conjugately-Matched Uniaxial Metamaterials Make Extremely Efficient Absorbers, Emitters, and Reflectors

The speed with which electromagnetic energy can be wirelessly transferred from a source to the user is a crucial parameter for performance of a large number of electronic and photonic devices. In this presentation we determine the constituent parameters of a medium which supports theoretically infinite energy concentration close to a medium sample surface; such a material combines properties of Perfectly Matched Layers (PML) and Double-Negative (DNG) media. It realizes conjugate matching with free space for every possible mode including, most importantly, all evanescent modes. We show that extremely high-amplitude resonating fields in the vicinity of a conjugately matched body can create large far-field radiation with the use of randomly placed particles which play the role of emission “vessels”

Surface plasmon-polaritons in graphene, embedded into medium with gain and losses

The paper deals with the theoretical consideration of surface plasmon-polaritons in the graphene monolayer, embedded into dielectric with spatially separated gain and losses. It is demonstrated, that presence of gain and losses in the system leads to the formation of additional mode of graphene surface plasmon-polaritons, which does not have its counterpart in the conservative system. When the gain and losses are mutually balanced, the position of exceptional point-transition point between unbroken and broken [Formula: see text]-symmetry-can be effectively tuned by graphene's doping. In the case of unbalanced gain and losses the spectrum of surface plasmon-polaritons contains spectral singularity, whose frequency is also adjustable through the electrostatic gating of graphene.European Commission through the project 'Graphene—Driven Revolutions in ICT and Beyond' (Ref. No. 785219), and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2019. Additionally, YVB acknowledges financing from FEDER and the portuguese Foundation for Science and Technology (FCT) through project PTDC/FIS-MAC/28887/201

New Self-Organization Route to Tunable Narrowband Optical Filters and Polarizers Demonstrated with ZnO–ZnWO4 Eutectic Composite

Electromagnetic fields interacting with microscopic structural features in a composite material provide emerging optical properties that surpass those offered by the individual components. However, composite materials can be generally lossy due to the scattering effects induced by inhomogeneities at the interfaces between different compounds. To overcome such problems, complicated and costly manufacturing procedures, such as top-down approaches, are generally required. In contrast, here ZnO–ZnWO4 eutectic self-organized composites grown by the micropulling method are considered, displaying sharp and strongly polarized transmission at 397 nm. Such an optical response is notable because it is not observed in either ZnO or ZnWO4 single crystals. The optical response is due to the refractive index matching of the two constituents, which self-organize into ordered structures via a micropulling down method. The optical behavior reported here can directly lead to applications, such as tunable narrowband filters with bandpass of 3 nm and polarizers, paving the way to a new self-organization route for manufacturing optical components