arXiv subjects

Fedor V. Kovalev

Publications and source records attributed to Fedor V. Kovalev.

3 recordsLinked to original sources

arXiv2025

Parametric metasurfaces for amplified up-conversion of electromagnetic waves

Spatiotemporal metasurfaces, characterized by dynamic variations in both space and time, enable functionalities unattainable with passive metasurfaces. In this study, we propose a novel concept of parametric metasurfaces capable of performing frequency up-conversion and amplification of free-space electromagnetic waves. This functionality is realized through the modulation of variable capacitances embedded in specially designed dual split-ring resonators. We explore various combinations of the pump and incident wave frequencies and investigate different operational regimes of the proposed parametric system. Our theoretical analysis reveals high up-conversion efficiency, with amplification levels exceeding 20 dB through a cascaded process, surpassing the limits set by the Manley-Rowe relations. Moreover, precise control over the phase of the up-converted waves is achieved by tuning the pump phase, paving the way for advanced manipulation of electromagnetic waves. This approach is applicable in the microwave and subterahertz ranges, with potential scalability to higher frequencies through ultrafast modulation techniques.

physics.optics↗

arXiv2024

Active Control of Bound States in the Continuum in Toroidal Metasurfaces

The remarkable properties of toroidal metasurfaces, featuring ultrahigh-Q bound states in the continuum (BIC) resonances and nonradiating anapole modes, have garnered significant attention. The active manipulation of quasi-BIC resonance characteristics offers substantial potential for advancing tunable metasurfaces. Our study explores explicitly the application of vanadium dioxide, a phase change material widely used in active photonics and room-temperature bolometric detectors, to control quasi-BIC resonances in toroidal metasurfaces. The phase change transition of vanadium dioxide occurs in a narrow temperature range, providing a large variation in material resistivity. Through heating thin film patches of vanadium dioxide integrated into a metasurface comprising gold split-ring resonators on a sapphire substrate, we achieve remarkable control over the amplitude and frequency of quasi-BIC resonances due to their high sensitivity to losses present in the system. Breaking the symmetry of meta-atoms reveals enhanced tunability. The predicted maximum change in the quasi-BIC resonance amplitude reaches 14 dB with a temperature variation of approximately 10 °C.

physics.optics↗

arXiv2024

Parametric metasurfaces for electromagnetic wave amplification

We study parametric amplification of electromagnetic waves using metasurfaces. We design a variable capacitor-loaded metasurface that can amplify incident electromagnetic waves. We analyze various regimes of operation of the system and find that we can achieve a significant gain (over 10 dB) in just one layer of such a structure, and this gain can be controlled by parametric modulation. We study the instability threshold for this system and show that a simple theoretical model agrees well with the results of full numerical simulations.

physics.app-ph↗