arXiv subjects

Mikhail S. Sidorenko

Publications and source records attributed to Mikhail S. Sidorenko.

3 recordsLinked to original sources

arXiv2023

Experimental demonstration of superdirective spherical dielectric antenna

An experimental demonstration of directivities exceeding the fundamental Kildal limit, a phenomenon called superdirectivity, is provided for spherical high-index dielectric antennas with an electric dipole excitation. A directivity factor of about 10 with a total efficiency of more than 80\% for an antenna having a size of a third of the wavelength was measured. High directivities are shown to be associated with constructive interference of particular electric and magnetic modes of an open spherical resonator. Both analytic solution for a point dipole and a full-wave rigorous simulation for a realistic dipole antenna were employed for optimization and analysis, yielding an excellent agreement between experimentally measured and numerically predicted directivities. The use of high-index low-loss ceramics can significantly reduce the physical size of such antennas while maintaining their overall high radiation efficiency. Such antennas can be attractive for various high-frequency applications, such as antennas for the Internet of things, smart city systems, 5G network systems, and others. The demonstrated concept can be scaled in frequency.

physics.class-ph↗

arXiv2023

Density of photonic states in aperiodic structures

Periodicity is usually assumed to be the necessary and sufficient condition for the formation of band gaps, i.e., energy bands with a suppressed density of states. Here, we check this premise by analyzing the band gap properties of three structures that differ in the degree of periodicity and ordering. We consider a photonic crystal, disordered lattice, and ordered but nonperiodic quasicrystalline structure. A real-space metric allows us to compare the degree of periodicity of these different structures. Using this metric, we reveal that the disordered lattice and the ordered quasicrystal can be attributed to the same group of material structures. We examine the density of their photonic states both theoretically and experimentally. The analysis reveals that despite their dramatically different degrees of periodicity, the photonic crystal and the quasicrystalline structure demonstrate an almost similar suppression of the density of states. Our results give new insight into the physical mechanisms resulting in the formation of band gaps.

physics.class-ph↗

arXiv2016

Two-Scale Approach to an Asymptotic Solution of Maxwell Equations in Layered Periodic Media

An asymptotic investigation of monochromatic electromagnetic fields in a layered periodic medium is carried out under the assumption that the wave frequency is close to the frequency of a stationary point of the dispersion surface. We find solutions of Maxwell equations by the method of two-scale asymptotic expansions. We establish that the principal order of the expansion of a solution dependent on three spatial coordinates is the sum of two differently polarized Floquet-Bloch solutions, each of which is multiplied by a slowly varying envelope function. We derive that the envelope functions satisfy a system of differential equations with constant coefficients. In new variables, it is reduced to a system of two independent equations, both of them are either hyperbolic or elliptic, depending on the type of the stationary point. The envelope functions are independent only in the planar case. Some consequences are discussed.

math-ph↗