arXiv subjects

Sergey Dyakov

Publications and source records attributed to Sergey Dyakov.

7 recordsLinked to original sources

arXiv2026

Anisotropic optical chirality and Lipkin's zilch tensor

Optical chirality density is widely used as a scalar measure for describing the chiral properties of electromagnetic fields and their interaction with isotropic chiral media. However, in anisotropic optically-active media, a single scalar quantity is generally insufficient to capture the full complexity of chiral field-matter coupling. In this work, we go beyond the conventional optical chirality density and introduce a tensor of electromagnetic chirality based on the Lipkin formalism. This tensor provides a richer and more physically transparent description of chiral electromagnetic fields, particularly in the context of their interaction with general magneto-electric media. We discuss the physical meaning of the individual tensor components and provide an expression for the excitation rate of small anisotropically chiral molecules in the presence anisotropically chiral fields.

physics.optics↗

arXiv2026

Beyond optical chirality density: tensor-based description of electromagnetic chirality

Optical chirality density is widely used as a local scalar measure of the chirality of an electromagnetic field and its interaction with isotropic chiral matter. However, within the dipole approximation, a general bi-anisotropic material response probes direction-dependent field bilinears that cannot, in general, be reduced to a single pseudoscalar. This necessitates the development of a systematic tensorial formulation to describe the coupling between arbitrary fields and general reciprocal bi-anisotropic media. To this end, we extend the Tang--Cohen formalism to a general anisotropic optical-activity pseudotensor, treating its trace and traceless symmetric and antisymmetric parts separately. We demonstrate while the trace part couples to classical optical chirality density, the traceless symmetric part is probed by the five Lipkin densities $Z^{ab0}$, which form part of the Lipkin tensor. On the other hand, for the antisymmetric part of the optical-activity pseudotensor, the coupling term is proportional to the reactive part of the local Poynting vector. Finally, we provide numerical examples of pseudo-chiral and anisotropic chiral electromagnetic fields and study their interaction with different bi-anisotropic media. The developed framework offers a systematic tensorial description of chiral and pseudo-chiral light-matter coupling. Importantly, our analysis identifies which specific field quantities must be enhanced to optimize the magneto-electric coupling in such media.

physics.optics↗

arXiv2026

Broadband wide-view all-dielectric handedness-preserving mirror

We report the theoretical design and experimental realization of a wideband, all-dielectric mirror that preserves the handedness of incident light upon reflection in the near-infrared range. The mirror consists of a high-contrast, near-subwavelength, one-dimensional dielectric grating on a Bragg mirror. We optimized this structure using a genetic algorithm and demonstrated its robustness against geometric imperfections and oblique incidence. Experimental reflection spectra measured under normal incidence in a circular polarization basis demonstrate a more than 100-nm-wide reflection band in which more than 98% of the reflected light preserves its handedness. The total reflection coefficient reached 80%. Furthermore, we demonstrate that the fabricated mirror maintains high performance even under oblique incidence for angles up to $\pm 15^\circ$. Owing to these unique characteristics, this mirror can serve as a reflective phase plate, making it an excellent candidate for the creation of a Fabry-P\'erot resonator for chiral light.

physics.optics↗

arXiv2025

The Fourier modal method for gratings with bi-anisotropic materials

We report an advanced formulation of the Fourier modal method developed for two-dimensionally periodic multilayered structures containing materials with non-zero macroscopic magneto-electric coefficients (also known as coefficients of chirality and bi-anisotropy) represented as arbitrary 3 by 3 tensors. We consider two numerical schemes for this formulation: with and without generalized Fourier factorization rules. For both schemes, we provide explicit expressions for the Fourier tensors of macroscopic material parameters and demonstrate that, in the absence of magneto-electric coupling, they reduce to the conventional factorization rules. We show that the scheme employing factorization rules facilitates improved convergence, even when the macroscopic chirality coefficient is large. The described formulation represents a fast and rigorous technique for theoretical studies of periodic structures with chiral, bi-anisotropic, or non-reciprocal materials in the widely used framework of the Fourier modal method.

physics.optics↗

arXiv2021

Resonant mode approximation of the scattering matrix of photonic crystal slabs near several Wood-Rayleigh anomalies

The resonant mode approximation of the scattering matrix is considered for calculating the optical properties of multilayered periodic structures within the formalism of the Fourier-modal method for two diffraction thresholds in close proximity of the spectral-angular range of interest. The developed approximation opens up possibilities for the fast calculation of the scattering matrix of these structures when describing the integral characteristics of spectra and dispersion curves containing high-Q resonances, such as bound states in the continuum.

physics.optics↗

arXiv2016

Ultra-sensitive label-free in-situ detection of dynamically driven self-assembly of 2D nanoplatelets on SOI chip

Fluid dispersed two-dimensional (2D) composite materials with dynamically tunable functional properties have recently emerged as a novel highly promising class of optoelectronic materials, opening up new routes not only for the emerging field of metamaterials but also to chip-scale multifunctional metadevices. However, in-situ monitoring and detection of the dynamic ordering of 2D nanoparticles on chip and during the device operation is still a huge challenge. Here we introduce a novel approach for on-chip, in-situ Raman characterisation of 2D-fluid composite materials incorporated into Si photonics chip. In this work the Raman signal for 2D nanoplatelets is selectively enhanced by Fabry-Perot resonator design of CMOS photonic-compatible microfluidic channels. This has then been extended to demonstrate the first in-situ Raman detection of the dynamics of individual 2D nanoplatelets, within a microfluidic channel. Our work paves the way for the first practicable realisation of 3D photonic microstructure shaping based on 2D-fluid composites and CMOS photonics platform.

cond-mat.mtrl-sci↗

arXiv2015

Thermal self-oscillations in radiative heat exchange

We report the effect of relaxation-type self-induced temperature oscillations in the system of two parallel plates of SiO$_2$ and VO$_2$ which exchange heat by thermal radiation in vacuum. The non-linear feedback in the self-oscillating system is provided by metal-insulator transition in VO$_2$. Using the method of fluctuational electrodynamics we show that under the action of an external laser of a constant power, the temperature of VO$_2$ plate oscillates around its phase transition value. The period and amplitude of oscillations depend on the geometry of the structure. We found that at 500\,nm vacuum gap separating bulk SiO$_2$ plate and 50 nm thick VO$_2$ plate, the period of self-oscillations is 2 s and the amplitude is 4 K which is determined by phase switching at threshold temperatures of phase transition.

physics.optics↗