arXiv subjects

Alina Karabchevsky

Publications and source records attributed to Alina Karabchevsky.

23 records · Page 2Linked to original sources

arXiv2019

Differential extinction of Vibrational Molecular Overtone Transitions with Gold Nanorods and Non-Trivial Surface Enhanced Near-IR Absorption (SENIRA)

Resonant coupling between plasmonic nanoantennas and molecular vibrational excitations is employed to amplify the weak overtone transitions that reside in the near-infrared. We explore for the first time the differential extinction of forbidden molecular overtone transitions coupled to the localized surface plasmons. We show that a non-trivial interplay between the molecular absorption enhancement and suppression of plasmonic absorption in a coupled system gives rise to orders of magnitude enhancement of the probe molecule differential extinction. Our results pave a road toward a new class of surface-enhanced near-infrared absorption-based sensors.

physics.optics↗

arXiv2019

Strong asymmetry of forward scattering effect from dielectric cubic nanoantenna in lossless media

Dielectric photonics platform provides unique possibilities to control light scattering via utilizing high-index dielectric nanoantennas with peculiar optical signatures. Despite the intensively growing field of all-dielectric nanophotonics, it is still unclear how surrounding media affect scattering properties of a nanoantenna with complex multipole response. Here we report on light scattering by a silicon cubic nanoparticles embedded in lossless media, supporting optical resonant response. We show that significant changes in the scattering process are governed by the electro-magnetic multipole resonances which experience spectral red-shift and broadening over the whole visible and near-infrared spectra as the indices of media increase. Most interestingly that the considered nanoantenna exhibits the broadband forward scattering in the visible and near-infrared spectral ranges due to the Kerker-effect in high-index media. The revealed effect of broadband forward scattering is essential for highly demanding applications in which the influence of the media is crucial such as health-care: sensing, treatment efficiency monitoring, and diagnostics. In addition, the insights from this study are expected to pave the way towards engineering the nanophotonic systems including but not limited to Huygens-metasurfaces in media within a single framework.

physics.optics↗

arXiv2018

Optomechanical manipulation with hyperbolic metasurfaces

Auxiliary nanostructures introduce additional flexibility into optomechanical manipulation schemes. Metamaterials and metasurfaces capable to control electromagnetic interactions at the near-field regions are especially beneficial for achieving improved spatial localization of particles, reducing laser powers required for trapping, and for tailoring directivity of optical forces. Here, optical forces acting on small particles situated next to anisotropic substrates, are investigated. A special class of hyperbolic metasurfaces is considered in details and is shown to be beneficial for achieving strong optical pulling forces in a broad spectral range. Spectral decomposition of the Green functions enables identifying contributions of different interaction channels and underlines the importance of the hyperbolic dispersion regime, which plays the key role in optomechanical interactions. Homogenised model of the hyperbolic metasurface is compared to its metal-dielectric multilayer realizations and is shown to predict the optomechanical behaviour under certain conditions related to composition of the top layer of the structure and its periodicity. Optomechanical metasurfaces open a venue for future fundamental investigations and a range of practical applications, where accurate control over mechanical motion of small objects is required.

physics.optics↗

arXiv2018

PT-symmetry breaking in multilayers with resonant loss and gain locks light propagation direction

Using the Maxwell-Bloch equations for resonantly absorbing and amplifying media, we study the temporal dynamics of light propagation through the PT-symmetric structures with alternating loss and gain layers. This approach allows us to precisely describe the response of the structure near the exceptional points of PT-symmetry breaking phase transition and, in particular, take into account the nonlinear effect of loss and gain saturation in the PT-symmetry broken state. We reveal that in this latter state the multilayer system possesses a lasing-like behavior releasing the pumped energy in the form of powerful pulses. We predict locking of pulse direction due to the PT-symmetry breaking, as well as saturation-induced irreversibility of phase transition and nonreciprocal transmission.

physics.optics↗

arXiv2017

Electromagnetically Induced Transparency in all-dielectric metamaterials due to nullifying of multipole moments

Here, we propose novel transparency effect in cylindrical all-dielectric metamaterials. We show that cancellation of multipole moments of the same kind lead to almost zero radiation losses due to the counter-directed multipolar moments in metamolecule. . Nullifying of multipoles, mainly dipoles and suppression of higher multipoles results in ideal transmission of incident wave through the designed metamaterial. The observed effect could pave the road to new generation of light-manipulating transparent metadevices such as filters, waveguides, cloaks and more.

physics.app-ph↗