Browsing by Author "Semchenko, Igor V."

Now showing 1 - 3 of 3

Broadband Reflectionless Metasheets: Frequency-Selective Transmission and Perfect Absorption
(2015) Asadchy, Viktar S.; Faniayeu, Ihar A.; "Ra'di", Y.; Khakhomov, Sergei A.; Semchenko, Igor V.; Tretyakov, Sergei A.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Energy of propagating electromagnetic waves can be fully absorbed in a thin lossy layer, but only in a narrow frequency band, as follows from the causality principle. On the other hand, it appears that there are no fundamental limitations on broadband matching of thin resonant absorbing layers. However, known thin absorbers produce significant reflections outside of the resonant absorption band. In this paper, we explore possibilities to realize a thin absorbing layer that produces no reflected waves in a very wide frequency range, while the transmission coefficient has a narrow peak of full absorption. Here we show, both theoretically and experimentally, that a thin resonant absorber, invisible in reflection in a very wide frequency range, can be realized if one and the same resonant mode of the absorbing array unit cells is utilized to create both electric and magnetic responses. We test this concept using chiral particles in each unit cell, arranged in a periodic planar racemic array, utilizing chirality coupling in each unit cell but compensating the field coupling at the macroscopic level. We prove that the concept and the proposed realization approach also can be used to create nonreflecting layers for full control of transmitted fields. Our results can have a broad range of potential applications over the entire electromagnetic spectrum including, for example, perfect ultracompact wave filters and selective multifrequency sensors.
Investigation of electromagnetic properties of a high absorptive, weakly reflective metamaterial - Substrate system with compensated chirality
(2017-01-07) Semchenko, Igor V.; Khakhomov, Sergei A.; Asadchy, V. S.; Golod, S. V.; Naumova, E. V.; Prinz, V. Ya; Goncharenko, A. M.; Sinitsyn, G. V.; Lyakhnovich, A. V.; Malevich, V. L.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In the present paper, a theoretical and experimental study of a highly absorptive, weakly reflective coating designed and fabricated on the basis of 3D THz resonant elements is reported. Transmission and reflection of electromagnetic waves from the metamaterial-substrate structure involving a highly absorptive, weakly reflective array of artificial bi-anisotropic elements were analyzed. The samples contained paired right-handed and left-handed helices, due to the fact that the chirality was compensated. The parameters of helices were optimized to achieve roughly identical values of dielectric permittivity and magnetic permeability. As a result, the metamaterial exhibited weak reflectivity in the vicinity of resonance frequency. On the other hand, effective resonance properties of the helices were tuned to ensure substantial absorption of THz radiation. Analytical expressions for the coefficients of radiation reflection and transmission in the samples were derived by solving a boundary-value problem for the propagation of electromagnetic waves in the metamaterial-substrate system. Simulated properties of fabricated structures were compared with experimental data.
Optical forces acting on a double dna-like helix, its unwinding and strands rupture
(2020-12) Semchenko, Igor V.; Mikhalka, Ivan S.; Faniayeu, Ihar A.; Khakhomov, Sergei A.; Balmakou, Aliaksei P.; Tretyakov, Sergei A.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this paper we study electromagnetic forces induced on DNA and DNA-like helices by external electromagnetic waves. We consider simultaneously occurring forces and torques, interconnected and acting along the double helix axis. Since the DNA molecule has an absorption band in the ultraviolet and visible range near wavelengths λ1res = 280 nm and λ2res = 500 nm, we expect that it may be possible to selectively apply engineered forces to DNA molecules using appropriate illumination by light in these frequency ranges. The optical forces are simulated for DNA fragments consisting of 20 and 35 turns. Fragments of this length are convenient for direct sequencing and subsequent use in experiments and in practice. It is shown that repulsion forces can arise between the strands of the double DNA-like helix in the field of external electromagnetic waves. Such forces are characteristic of a DNA-like helix with its specific pitch angle and are not inherent in double helices with more straightened or more compressed turns. These repulsion forces, acting along the entire helix, both for electric charges and for electric currents, can lead to damage and rupture of the strands in the double helix. In addition, there can also exist forces and moments of forces directed along the helix axis, which simultaneously stretch and unwind a double helix. The double helix equilibrium under the action of optical forces is also of interest from another point of view, i.e., for optimizing the structure of artificial magnetics and bianisotropic metamaterials for applications in all frequency ranges.