arXiv subjects

A. A. Bogdanov

Publications and source records attributed to A. A. Bogdanov.

At least 19 recordsLinked to original sources

arXiv2026

A complete photoluminescence polarization palette from a photonic-crystal slab

Integrated light sources with tailored polarization are essential for integrated photonics, optical communication, sensing, and structured-light applications. However, generating a broad set of polarization states from spontaneous emission usually relies on structures with broken mirror, rotational, or inversion symmetries, or on emitters with predefined polarization properties. Here, we demonstrate a complete photoluminescence polarization palette in a single achiral photonic-crystal slab with a hexagonal lattice of holes and embedded self-assembled Ge(Si) nanoislands. We show that the polarization of the emitted light is governed by the interplay among modes with different symmetries rather than by the properties of unpolarized emitters. Along the high-symmetry directions of the Brillouin zone, symmetry enforces purely linear emission and enables direct polarization-based classification of the photonic-crystal modes. Away from these directions, all Stokes parameters become non-zero, providing full-Stokes control of photoluminescence and highly polarized emission. We further demonstrate polarization vortices associated with symmetry-protected and Friedrich-Wintgen bound states in the continuum, as well as radiating polarization singularities not associated with bound states in the continuum. Through appropriate geometric optimization, the same platform supports photoluminescence with a full polarization palette as well as polarization vortices. Our results establish achiral photonic-crystal slabs as monolithic sources of symmetry-programmable photoluminescence polarization.

physics.optics↗

arXiv2024

Engineering whispering gallery modes in MoSe$_2$/WS$_2$ double heterostructure nanocavities: Towards developing all-TMDC light sources

Transition metal dichalcogenides (TMDCs) have emerged as highly promising materials for nanophotonics and optoelectronics due to their exceptionally high refractive indices, strong excitonic photoluminescence (PL) in monolayer configurations, and the versatility to engineer van der Waals (vdW) heterostructures. In this work, we exploit the intense excitonic PL of a MoSe$_2$ monolayer combined with the high refractive index of bulk WS$_2$ to fabricate microdisk cavities with tunable light emission characteristics. These microdisks are created from a 50-nm-thick WS$_2$/MoSe$_2$/WS$_2$ double heterostructure using frictional mechanical scanning probe lithography. The resulting cavities achieve a 4-10-fold enhancement in excitonic PL from the MoSe$_2$ monolayer at wavelengths near 800 nm. The excitonic PL peak is modulated by sharp spectral features, which correspond to whispering gallery modes (WGMs) supported by the cavity. A microdisk with a diameter of 2.35 $μ$m demonstrates WGMs with a quality factor of up to 700, significantly surpassing theoretical predictions and suggesting strong potential for lasing applications. The spectral positions of the WGMs can be finely tuned by adjusting the microdisk's diameter and thickness, as confirmed by theoretical calculations. This approach offers a novel route for developing ultra-compact, all-TMDC double heterostructure light sources with record-small size.

physics.optics↗

arXiv2024

An Approach to Gamma-Hadron Separation via Measurements of the Middle-UV Fraction of EAS emission by an Imaging Atmospheric Cherenkov Telescope with UV-Sensitive SiPM detectors

The operation of a small-size Cherenkov gamma-ray telescope TAIGA-IACT with camera on SiPMs OnSemi MicroFJ-60035 has been modelled by multiparticle Monte Carlo (MC) methods. The model implies that telescope camera is equipped with two specific types of filters of 290-590 nm (visible+NUV) and 220-320 nm (MUV+UVB)-bands, each covering half of the camera pixels in some uniform order. This allows one to measure the fraction of UV-radiation in total amount of Cherenkov radiation of an extensive air shower (EAS), that can be used for efficient gamma-hadron separation. The corresponding quality factor takes values up to 5.07 in the 10-100 TeV range depending on the distance to EAS axis and camera orientation.

astro-ph.HE↗

arXiv2023

Room-temperature exceptional-point-driven polariton lasing from perovskite metasurface

Excitons in lead bromide perovskites exhibit high binding energy and high oscillator strength, allowing for a strong light-matter coupling regime in the perovskite-based cavities localizing photons at the nanoscale. This opens up the way for the realization of exciton-polariton Bose-Einstein condensation and polariton lasing at room temperature -- the inversion-free low-threshold stimulated emission. However, polariton lasing in perovskite planar photon cavities without Bragg mirrors has not yet been observed and proved experimentally. In this work, we employ perovskite metasurface, fabricated with nanoimprint lithography, supporting so-called exceptional points to demonstrate the room-temperature polariton lasing. The exceptional points in exciton-polariton dispersion of the metasurface appear upon optically pumping in the nonlinear regime in the spectral vicinity of a symmetry-protected bound state in the continuum providing high mode confinement with the enhanced local density of states beneficial for polariton condensation. The observed lasing emission possesses high directivity with a divergence angle of around 1$^\circ$ over one axis. The employed nanoimprinting approach for solution-processable large-scale polariton lasers is compatible with various planar photonic platforms suitable for on-chip integration.

physics.optics↗

arXiv2020

Polarization-controlled selective excitation of Mie resonances of dielectric nanoparticle on a coated substrate

High-index spherical nanoparticles with low material losses support sharp high-Q electric and magnetic resonances and exhibit a number of interesting optical phenomena. Developments in fabrication techniques have enabled the further study of their properties and the investigation of related optical effects. After deposition on a substrate, the optical properties of a particle change dramatically due to mutual interaction. Here, we consider a silicon spherical nanoparticle on a dielectric one-layered substrate. At the normal incidence of light, the layer thickness controls the contribution of the nanoparticle's electric and magnetic multipoles to the subsequent optical response. We show that changing the polarization of incident light at a specific excitation angle and layer thickness leads to switching between the multipoles. We further observe a related polarization-driven control over the direction of the scattered radiation.

physics.optics↗

arXiv2020

Multipolar engineering of subwavelength dielectric particles for scattering enhancement

Electromagnetic scattering on subwavelength structures keeps attracting attention owing to abroad range of possible applications, where this phenomenon is in use. Fundamental limits of scattering cross-section, being well understood in spherical geometries, are overlooked in cases of low-symmetry resonators. Here, we revise the notion of superscattering and link this property with symmetry groups of the scattering potential. We demonstrate pathways to spectrally overlap several eigenmodes of a resonator in a way they interfere constructively and enhance the scattering cross-section. As a particular example, we demonstrate spectral overlapping of several electric and magnetic modes in a subwavelength entirely homogeneous ceramic resonator. The optimized structures show the excess of a dipolar scattering cross-section limit for a sphere up to a factor of four. The revealed rules, which link symmetry groups with fundamental scattering limits, allow performing and assessing designs of subwavelength supperscatterers, which can find a use in label-free imaging, compact antennas, long-range radio frequency identification, and many other fields.

physics.class-ph↗

arXiv2020

Observation of an accidental bound state in the continuum in a chain of dielectric disks

Being a general wave phenomenon, bound states in the continuum (BICs) appear in acoustic, hydrodynamic, and photonic systems of various dimensionalities. Here, we report the first experimental observation of an accidental electromagnetic BIC in a one-dimensional periodic chain of coaxial ceramic disks. We show that the accidental BIC manifests itself as a narrow peak in the transmission spectra of the chain placed between two loop antennas. We demonstrate a linear growth of the radiative quality factor of the BICs with the number of disks that is well-described with a tight-binding model. We estimate the number of the disks when the radiation losses become negligible in comparison to material absorption and, therefore, the chain can be considered practically as infinite. The presented analysis is supported by near-field measurements of the BIC profile. The obtained results provide useful guidelines for practical implementations of structures with BICs opening new horizons for the development of radio-frequency and optical metadevices.

physics.class-ph↗

arXiv2019

Dyakonov-like surface waves in anisotropic cylindrical waveguides

Dyakonov surface waves are a well-known example of surface electromagnetic waves propagating along a plane interface between isotropic and anisotropic dielectric media. Here, we investigate the spectrum and radiative losses of Dyakonov waves at the curved interface considering both cases of "positive" and "negative" curvature of anisotropic medium. We demonstrate how Dyakonov waves at a plane interface continuously transform to the leaky or guided modes of an anisotropic cylindrical waveguide and simple derive asymptotic equation for radiative losses. All analytical results are confirmed by solving exact dispersion equation numerically. We believe that our work extends the potential practical application of Dyakonov waves in optics and photonics devices.

physics.optics↗

arXiv2018

Bound states in the continuum and Fano resonances in the strong mode coupling regime

The study of resonant dielectric nanostructures with high refractive index is a new research direction in nanoscale optics and metamaterial-inspired nanophotonics. Because of the unique optically-induced electric and magnetic Mie resonances, high-index nanoscale structures are expected to complement or even replace different plasmonic components in a range of potential applications. Here we study strong coupling between modes of a single subwavelength high-index dielectric resonator and analyse the mode transformation and Fano resonances when resonator's aspect ratio varies. We demonstrate that strong mode coupling results in resonances with high quality factors, which are related to the physics of bound states in the continuum when the radiative losses are almost suppressed due to the Friedrich-Wintgen scenario of destructive interference. We explain the physics of these states in terms of multipole decomposition and show that their appearance is accompanied by drastic change of the far-field radiation pattern. We reveal a fundamental link between the formation of the high-quality resonances and peculiarities of the Fano parameter in the scattering cross-section spectra. Our theoretical findings are confirmed by microwave experiments for the scattering of a high-index cylindrical resonators with a tunable aspect ratio. The proposed mechanism of the strong mode coupling in single subwavelength high-index resonators accompanied by resonances with high quality factor helps to extend substantially functionalities of all-dielectric nanophotonics that opens new horizons for active and passive nanoscale metadevices.

physics.optics↗

arXiv2018

Experimental observation of symmetry protected bound state in the continuum in a chain of dielectric disks

Existence of bound states in the continuum (BIC) manifests a general wave phenomenon firstly predicted in quantum mechanics in 1929 by J. von Neumann and E. Wigner. Today it is being actively explored in photonics, radiophysics, acoustics, and hydrodynamics. In this paper, we report the first experimental observation of electromagnetic bound state in the radiation continuum in 1D array of dielectric particles. By measurement of the transmission spectra of the ceramic disk chain at GHz frequencies we demonstrate how a resonant state in the vicinity of the center of the Brillouin zone turns into a symmetry-protected BIC with increase the number of the disks. We estimate a number of the disks when the radiation losses become negligible in comparison to material absorption and, therefore, the chain could be considered practically as infinite. The presented analysis is supplemented by measurements of the near fields of the symmetry protected BIC. All measurements are in a good agreement with the results of numerical simulation and analytical model based on tight-binding approximation. The obtained results provide useful guidelines for practical implementations of structures with bound states in the continuum that opens up new horizons for the development of optical and radiofrequency metadevices.

physics.app-ph↗

arXiv2018

Nonlinear Bound States in the Continuum in One-Dimensional Photonic Crystal Slab

Optical bound state in the continuum (BIC) is characterized by infinitely high quality factor resulting in drastic enhancement of light-matter interaction phenomena. We study the optical response of a one-dimensional photonic crystal slab with Kerr focusing nonlinearity in the vicinity of BIC analytically and numerically. We predict a strong nonlinear response including multistable behaviour, self-tuning of BIC to the frequency of incident wave, and breaking of symmetry protected BIC. We show that all of these phenomena can be observed in silicon photonic structure at the pump power of several $μ$W/cm$^2$. We also analyze the modulation instability of the obtained solutions and the effect of the finite size of the structure on the stability. Our findings have strong implications for nonlinear photonics and integrated optical circuits.

physics.optics↗

arXiv2018

Strong coupling between excitons in transition metal dichalcogenides and optical bound states in the continuum

Being motivated by recent achievements in the rapidly developing fields of optical bound states in the continuum (BICs) and excitons in monolayers of transition metal dichalcogenides, we analyze strong coupling between BICs in $\rm Ta_2O_5$ periodic photonic structures and excitons in $\rm WSe_2$ monolayers. We demonstrate that giant radiative lifetime of BICs allow to engineer the exciton-polariton lifetime enhancing it three orders of magnitude compared to a bare exciton. We show that maximal lifetime of hybrid light-matter state can be achieved at any point of $\mathbf{k}$-space by shaping the geometry of the photonic structure. Our findings open new route for the realization of the moving exciton-polariton condensates with non-resonant pump and without the Bragg mirrors which is of paramount importance for polaritonic devices.

cond-mat.mes-hall↗

arXiv2017

Comparative study of the inclusive asymmetries induced by polarized protons and antiprotons at 16 GeV/$c$ at the U-70 accelerator

The only comparative study of the inclusive pion single-spin asymmetries produced in the interactions of the polarized protons and antiprotons in collisions with unpolarized proton was carried out at E-704 experiment. Significant asymmetries were found at large $x_{F}$ and middle $p_{T}$, $π^{+}$ and $π^{0}$ asymmetries have positive signs while $π^{-}$ has negative one in the $p^{\uparrow}+p$ collisions, while in the $\bar{p}^{\uparrow}+p$ interactions the $π^{-}$ and $π^{0}$ asymmetries have positive signs while $π^{+}$ has negative sign. Similar experimental study can be done in the SPASCHARM experiment at U-70 accelerator at IHEP for various secondary particles with the use of 16 GeV polarized proton and antiproton beams.

hep-ex↗

arXiv2017

Excitonic lasing of strain-free InP(As) quantum dots in AlInAs microdisk

Formation, emission and lasing properties of strain-free InP(As)/AlInAs quantum dots (QDs) embedded in AlInAs microdisk (MD) cavity were investigated using transmission electron microscopy and photoluminescence (PL) techniques. In MD structures, the QDs having nano-pan-cake shape have height of ~2 nm, lateral size of 20-50 nm and density of ~5x109 cm-2. Their emission observed at ~940 nm revealed strong temperature quenching, which points to exciton decomposition. It also showed unexpected type-I character indicating In-As intermixing, as confirmed by band structure calculations. We observed lasing of InP(As) QD excitons into whispering gallery modes in MD having dimeter ~3.2 mkm and providing free spectral range of ~27 nm and quality factors up to Q~13000. Threshold of ~50 W/cm2 and spontaneous emission coupling coefficient of ~0.2 were measured for this MD-QD system.

physics.optics↗

arXiv2016

Tamm-Langmuir surface waves

In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states - we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.

physics.optics↗

arXiv2016

Surface plasmon polariton assisted optical pulling force

We demonstrate both analytically and numerically the existence of optical pulling forces acting on particles located near plasmonic interfaces. Two main factors contribute to the appearance of this negative reaction force. The interference between the incident and reflected waves induces a rotating dipole with an asymmetric scattering pattern while the directional excitation of surface plasmon polaritons (SPP) enhances the linear momentum of scattered light. The strongly asymmetric SPP excitation is determined by spin-orbit coupling of the rotating dipole and surface plasmon polariton. As a result of the total momentum conservation, the force acting on the particle points in a direction opposite to the incident wave propagation. We derive analytical expressions for the force acting on a dipolar particles placed in the proximity of plasmonic surfaces. Analytical expressions for this pulling force are derived within the dipole approximation and are in excellent agreement with results of electromagnetic numerical calculations. The forces acting on larger particles are analyzed numerically, beyond the dipole approximation.

physics.optics↗

arXiv2016

Dark-field imaging as a non-invasive method for characterization of whispering gallery modes in microdisk cavities

Whispering gallery mode microdisk cavities fabricated by direct laser writing are studied using dark-field imaging and spectroscopy in the visible spectral range. {Dark-field imaging allows us to directly visualize the spatial intensity distribution of whispering gallery modes. We extract their azimuthal and radial mode indices from dark-field images, and find the axial mode number from the dispersion relation. The scattering spectrum obtained in the confocal arrangement provides information on the density of optical states in the resonator. The proposed technique is a simple non-invasive way to characterize the optical properties of microdisk cavities.

physics.optics↗

arXiv2015

Mode selection in InAs quantum dot microdisk lasers using focused ion beam technique

Optically pumped InAs quantum dot microdisk lasers with grooves etched on their surface by a focused ion beam is studied. It is shown that the radial grooves, depending on their length, suppress the lasing of specific radial modes of the microdisk. Total suppression of all radial modes except for the fundamental radial one is also demonstrated. The comparison of laser spectra measured at 78 K before and after ion beam etching for microdisk of 8 $μ$m in diameter shows a six-fold increase of mode spacing, from 2.5 nm to 15.5 nm, without significant decrease of the dominant mode quality factor. Numerical simulations are in good agreement with experimental results.

physics.optics↗