arXiv subjects

Sergey Kruk

Publications and source records attributed to Sergey Kruk.

24 records · Page 2Linked to original sources

arXiv2019

Photosensitive chalcogenide metasurfaces supporting bound states in the continuum

We study, both theoretically and experimentally, tunable metasurfaces supporting sharp Fano-resonances inspired by optical bound states in the continuum. We explore the use of arsenic trisulfide (a photosensitive chalcogenide glass) having optical properties which can be finely tuned by light absorption at the post-fabrication stage. We select the resonant wavelength of the metasurface corresponding to the energy below the arsenic trisulfide bandgap, and experimentally control the resonance spectral position via exposure to the light of energies above the bandgap.

physics.optics↗

arXiv2019

Individual nanoantennas empowered by bound states in the continuum for nonlinear photonics

Bound states in the continuum (BICs) represent localized modes with energies embedded in the continuous spectrum of radiating waves. BICs were discovered initially as a mathematical curiosity in quantum mechanics, and more recently were employed in photonics. Pure mathematical bound states have infinitely-large quality factors (Q factors) and zero resonant linewidth. In optics, BICs are physically limited by a finite size, material absorption, structural disorder, and surface scattering, and they manifest themselves as the resonant states with large Q factors, also known as supercavity modes or quasi-BICs. Optical BIC resonances have been demonstrated only in extended 2D and 1D systems and have been employed for distinct applications including lasing and sensing. Optical quasi-BIC modes in individual nanoresonators have been discovered recently but they were never observed in experiment. Here, we demonstrate experimentally an isolated subwavelength nanoresonator hosting a quasi-BIC resonance. We fabricate the resonator from AlGaAs material on an engineered substrate, and couple to the quasi-BIC mode using structured light. We employ the resonator as a nonlinear nanoantenna and demonstrate record-high efficiency of second-harmonic generation. Our study brings a novel platform to resonant subwavelength photonics.

physics.optics↗

arXiv2019

Third-harmonic generation in photonic topological metasurfaces

We study nonlinear effects in two-dimensional photonic metasurfaces supporting topologically-protected helical edge states at the nanoscale. We observe strong third-harmonic generation mediated by optical nonlinearities boosted by multipolar Mie resonances of silicon nanoparticles. Variation of the pump-beam wavelength enables independent high-contrast imaging of either bulk modes or spin-momentum-locked edge states. We demonstrate topology-driven tunable localization of the generated harmonic fields and map the pseudospin-dependent unidirectional waveguiding of the edge states bypassing sharp corners. Our observations establish dielectric metasurfaces as a promising platform for the robust generation and transport of photons in topological photonic nanostructures.

physics.optics↗

arXiv2017

Transparent dielectric metasurfaces for mode modulation and spatial multiplexing

Expanding the use of physical degrees of freedom to employ spatial multiplexing of data in optical communication is considered the most disruptive and effective solution to meet the capacity demand of the growing information traffic. Development of space-division-multiplexing methods stimulated research on spatial modulation, detection and processing of data, attracting interest from various fields of science. A passive all-dielectric metasurface with near-unity transmission is used to engineer spatial mode profiles, potentially of arbitrary complexity. The broadband response of the metasurface covers S, C, and L bands of fibre communications. Unlike conventional phase plates, the metasurface allows for both phase and polarization conversion, providing full flexibility for mode engineering. We employ the metasurface for both mode modulation and mode multiplexing in free-space optical communication, and demonstrate that it is capable of mode multiplexing with an extinction ratio in excess of 20 dB over the whole C-band with negligible penalty even for 100 Gb/s DP-QPSK signals. These results merge two seemingly different fields, optical communication and metamaterials, and suggest a novel approach for ultimate miniaturisation of mode multiplexers and advanced LiFi technologies.

physics.optics↗

arXiv2017

Functional meta-optics and nanophotonics govern by Mie resonances

Scattering of electromagnetic waves by subwavelength objects is accompanied by the excitation of electric and magnetic Mie resonances, that may modify substantially the scattering intensity and radiation pattern. Scattered fields can be decomposed into electric and magnetic multipoles, and the magnetic multipoles define magnetic response of structured materials underpinning the new field of all-dielectric resonant meta-optics. Here we review the recent developments in meta-optics and nanophotonics, and demonstrate that the Mie resonances can play a crucial role offering novel ways for the enhancement of many optical effects near magnetic and electric multipolar resonances, as well as driving a variety of interference phenomena which govern recently discovered novel effects in nanophotonics. We further discuss the frontiers of all-dielectric meta-optics for flexible and advanced control of light with full phase and amplitude engineering, including nonlinear nanophotonics, anapole nanolasers, quantum tomography, and topological photonics.

physics.optics↗

arXiv2016

Broadband highly-efficient dielectric metadevices for polarization control

Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. By employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-plates that can operate across multiple telecom bands with ~99% polarization conversion efficiency.

physics.optics↗