arXiv subjects

Ilia Smagin

Publications and source records attributed to Ilia Smagin.

3 recordsLinked to original sources

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

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

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↗