Miniature Wireless Power Transfer System for Charging Vertically Oriented Receivers

Development of compact wireless power transfer (WPT) systems for charging miniature randomly oriented electronic devices is quite a challenge. Traditionally, WPT systems based on resonant magnetic coupling utilize face-to-face aligned transmitter and receiver coils providing sufficient efficiency at relatively large distances. However, with the presence of angular receiver misalignment in a such system, the mutual coupling decreases resulting in a low power transfer efficiency. Here we develop a compact WPT system for wireless charging of miniature receivers vertically oriented with respect to the transmitter. As a transmitter, we employ a butterfly coil that provides a strong tangential component of the magnetic field. Thus, a vertically oriented receiver located in the magnetic field can be charged wirelessly. We perform numerical and experimental studies of the WPT system power transfer efficiency as a function of the distance between the transmitter and the receiver. The misalignment and rotation dependencies of power transfer efficiency are also experimentally studied. We demonstrate the power transfer efficiency of 60 % within transfer distance of 4 mm for a vertically oriented receiver with an overall dimension of 20 mm X 14 mm at the frequency of 6.78 MHz

Giant field enhancement in high-index dielectric subwavelength particles

Besides purely academic interest, giant field enhancement within subwavelength particles at light scattering of a plane electromagnetic wave is important for numerous applications ranging from telecommunications to medicine and biology. In this paper, we experimentally demonstrate the enhancement of the intensity of the magnetic field in a high-index dielectric cylinder at the proximity of the dipolar Mie resonances by more than two orders of magnitude for both the TE and TM polarizations of the incident wave. We present a complete theoretical explanation of the effect and show that the phenomenon is very general - it should be observed for any high-index particles. The results explain the huge enhancement of nonlinear effects observed recently in optics, suggesting a new landscape for all-dielectric nonlinear nanoscale photonics.Comment: 8 pages, 4 figure

Circularly polarized antenna for coherent manipulation of NV-centers in diamond

Dielectric resonator antenna with circular polarization of microwave magnetic field for efficient, coherent and uniform spin manipulation at nitrogen-vacancy centers in diamond is discussed. The results of numerical simulations of the microwave magnetic field generated by the antenna are reported and analyzed. The uniform magnetic field with circular polarization is obtained inside the antenna. Using the simulated amplitude of the magnetic field inside the antenna the Rabi frequency is estimated. The Rabi frequency of 41 MHz with inhomogeneity less then 1 % for the diamond volume of 3 mm3 is demonstrated under 10 W of input microwave power.This work was supported by the Russian Science Foundation (Grant 16-19-10367)

Generalized Huygens' metasurface based on higher order magnetic dipolar resonances

All-dielectric Huygens’ metasurface composed of hollow cubic-shape unit cells supporting higher order magnetic resonances is demonstrated. Due to the combination of the electric and magnetic Mie-type multipolar resonances of the unit cell the metasurface exhibits an evident multimode interference with three pronounced maxima/minima in the transmission/reflection spectrum together with the multimode unidirectional scattering when the Kerker conditions are satisfied.This work was supported by Russian Science Foundation (Project No. 17-19-01731). P.K. and P.B. acknowledge the scholarship and grant of the President of Russian Federation. A.M. was supported by the Australian Research Council

Broadband isotropic μ-near-zero metamaterials

Natural diamagnetism, while being a common phenomenon, is limited to permeability values close to unity. Artificial diamagnetics, to the contrary, can be engineered to provide much lower values and may even possess an effective permeability close to zero. In this letter, we provide an experimental confirmation of the possibility to obtain extremely low permeability values by manufacturing an isotropic metamaterial composed of conducting cubes. We show that the practical assembly is quite sensitive to fabrication tolerances and demonstrate that permeability of about μ=0.15 is realisable.This work was supported by the Ministry of Education and Science of Russian Federation (Project 11.G34.31.0020), Dynasty Foundation (Russia), grant of the President of Russian Federation, and by the Australian Research Council (CUDOS Centre of Excellence CE110001018)

Invisibility and perfect absorption of all-dielectric metasurfaces originated from the transverse Kerker effect

Dielectric metasurfaces perform unique photonics effects and serve as the engine of nowadays light-matter technologies. Here, we suggest theoretically and demonstrate experimentally the realization of a high transparency effect in a novel type of all-dielectric metasurface, where each constituting meta-atom of the lattice presents the so-called transverse Kerker effect. In contrast to Huygens' metasurfaces, both phase and amplitude of the incoming wave remain unperturbed at the resonant frequency and, consequently, our metasurface totally operates in the invisibility regime. We prove experimentally, for the microwave frequency range, that both phase and amplitude of the transmitted wave from the metasurface remain almost unaffected. Finally, we demonstrate both numerically and experimentally and explain theoretically in detail a novel mechanism to achieve perfect absorption of the incident light enabled by the resonant response of the dielectric metasurfaces placed in the vicinity of a conducting substrate. In the subdiffractive limit, we show the aforementioned effects are mainly determined by the optical response of the constituting meta-atoms rather than the collective lattice contributions. With the spectrum scalability, our findings can be incorporated in engineering devices for energy harvesting, nonlinear phenomena and filters applications.Comment: 10 pages, 6 figure

Competing nonlinearities with metamaterials

We suggest an approach for creating metamaterials with sign-varying nonlinear response. We demonstrate that microwavemetamaterials with such competing nonlinearities can be created by loading split-ring resonators (“meta-atoms” of the structure) with pairs of varactor diodes and photodiodes exhibiting nonmonotonic resonance frequency shift with changing incident microwave power. Additionally, the nonlinear response of such metamaterials can be controlled by illuminating the meta-atoms by light.This work was supported by the Ministry of Education and Science of Russia, projects 11.G34.31.0020, 14.B37.21.1176 and 14.B37.21.1283, Scholarship of the President of the Russian Federation for young scientists and graduate students, Russian Foundation for Basic Research (RFBR), Dynasty Foundation (Russia) and the Australian Research Council (Australia)