arXiv subjects

Daria A. Smirnova

Publications and source records attributed to Daria A. Smirnova.

At least 19 recordsLinked to original sources

arXiv2026

Chiral lasing via broken parity-time symmetry in bound-state-in-the-continuum metasurfaces

We propose a concept for chiral lasing from planar metasurfaces that obviates the need for traditional out-of-plane symmetry breaking by exploiting spatial gain-loss modulation to break parity-time symmetry. We explain the underlying non-Hermitian physics of this design principle using a coupled-mode model of a four-site plaquette. The symmetry requirements for such chiral emission are explained with a general symmetry analysis based on projection operator matrices, implemented algorithmically for automated evaluation. This method enables the design of planar metasurfaces capable of emitting nearly-pure circularly polarized light. We apply our analysis to simulations of both symmetric and asymmetric versions of a Fylfot metasurface design and demonstrate that the gain mode at the parity-time symmetric exceptional point exhibits chiral emission. Lastly, we present a readily manufacturable metasurface made from an InGaAs slab, showing that such a metasurface laser can be actively tuned from linear to circular polarization.

physics.optics↗

arXiv2025

Momentum-space non-Hermitian skin effect in an exciton-polariton system

Localization of a macroscopic number of eigenstates on a real-space boundary, known as the non-Hermitian skin effect, is one of the striking topological features emerging from non-Hermiticity. Realizing this effect typically requires periodic (lattice) systems with asymmetry of intersite coupling, which is not readily available in many physical platforms. Instead, it is meticulously engineered, e.g., in photonics, which results in complex structures requiring precise fabrication steps. Here, we propose a simpler mechanism: introducing an asymmetric, purely imaginary potential in a topologically trivial system induces momentum-space localization akin to the skin effect. We experimentally demonstrate this localization using exciton polaritons, hybrid light-matter quasi-particles in a simple engineered `round box' trap, pumped by a laser pump offset from the trap center. The effect disappears if the pump is concentric with the trap. The localization persists and becomes stronger at higher densities of polaritons, when a non-equilibrium Bose-Einstein condensate is formed and the system becomes nonlinear. Our approach offers a new route to realizing skin effects in continuous, non-periodic systems and exploring the interplay of non-Hermiticity, topology, and nonlinearity in macroscopic quantum states.

physics.optics↗

arXiv2024

Non-Hermitian excitations in nonlinear topological lattice

Non-linear effects and non-Hermitian phenomena unveil additional intricate facets in topological matter physics. They can naturally intertwine to enable advanced functionalities in topoelectrical circuits and photonic structures. Here, we illustrate the subtle interplay between nonlinearity and non-Hermiticity by examining the characteristics of small wave perturbations on the background of the self-induced topological edge state in the nonlinear Su-Schrieffer-Heeger model. We demonstrate that their underlying physics is captured by the non-Hermitian effective Hamiltonian, which features nonreciprocal coupling terms and entails unconventional time-dependent field localization.

physics.optics↗

arXiv2023

Water-Wave Vortices and Skyrmions

Topological wave structures -- phase vortices, skyrmions, merons, etc. -- are attracting enormous attention in a variety of quantum and classical wave fields. Surprisingly, these structures have never been properly explored in the most obvious example of classical waves: water-surface (gravity-capillary) waves. Here we fill this gap and describe: (i) water-wave vortices of different orders carrying quantized angular momentum with orbital and spin contributions, (ii) skyrmion lattices formed by the instantaneous displacements of the water-surface particles in wave interference, (iii) meron (half-skyrmion) lattices formed by the spin density vectors, as well as (iv) spatiotemporal water-wave vortices and skyrmions. We show that all these topological entities can be readily generated in linear water-wave interference experiments. Our findings can find applications in microfluidics and show that water waves can be employed as an attainable playground for emulating universal topological wave phenomena.

physics.flu-dyn↗

arXiv2023

Identifying topology of leaky photonic lattices with machine learning

We show how machine learning techniques can be applied for the classification of topological phases in leaky photonic lattices using limited measurement data. We propose an approach based solely on bulk intensity measurements, thus exempt from the need for complicated phase retrieval procedures. In particular, we design a fully connected neural network that accurately determines topological properties from the output intensity distribution in dimerized waveguide arrays with leaky channels, after propagation of a spatially localized initial excitation at a finite distance, in a setting that closely emulates realistic experimental conditions.

physics.optics↗

arXiv2023

Self-steepening-induced stabilization of nonlinear edge waves at photonic valley-Hall interfaces

Localized nonlinear modes at valley-Hall interfaces in staggered photonic graphene can be described in the long-wavelength limit by a nonlinear Dirac-like model including spatial dispersion terms. It leads to a modified nonlinear Schrödinger equation for the wave field amplitude that remarkably incorporates a nonlinear velocity term. We show that this nonlinear velocity correction results in a counter-intuitive stabilization effect for relatively high-amplitude plane-wave-like edge states, which we confirm by calculation of complex-valued small-amplitude perturbation spectra and direct numerical simulation of propagation dynamics in staggered honeycomb waveguide lattices with on-site Kerr nonlinearity. Our findings are relevant to a variety of nonlinear photonic systems described by Dirac-like Hamiltonians.

physics.optics↗

arXiv2022

Boosting Topological Zero Modes Using Elastomer Waveguide Arrays

We employ the Su-Schrieffer-Heeger model in elastic polymer waveguide arrays to design and realize travelling topologically protected modes. The observed delocalization of the optical field for superluminal defect velocities agrees well with theoretical descriptions. We apply mechanical strain to modulate the lattices' coupling coefficient. This work demonstrates a novel platform for rapid prototyping of topological photonic devices and establishes strain-tuning as a viable design parameter for topological waveguide arrays.

physics.optics↗

arXiv2022

Reconfigurable topological states in arrays of bianisotropic particles

Topological photonics promotes a novel approach to resilient light manipulation by exploiting spatio-temporal symmetries of the system and dual symmetry of electromagnetic field. Various prospective device applications pose the need to flexibly control robust field localization associated with topological modes. Here we design a topological array of resonant dielectric meta-atoms with bianisotropic response induced by a spatial symmetry reduction. Mutual orientation of the designed meta-atoms encodes a staggered bianisotropy pattern capable of trapping topological states in a one-dimensional array containing a small number of particles. We show that the topological interface state can be tailored by the rotation of coaxial bianisotropic particles arranged in an equidistant lattice. Our experimental implementation based on ceramic horseshoe-shaped disks demonstrates remarkable reconfigurability of electromagnetic topological states.

physics.app-ph↗

arXiv2021

Nonlinear signatures of Floquet band topology

We study how the nonlinear propagation dynamics of bulk states may be used to distinguish topological phases of slowly-driven Floquet lattices. First, we show how instabilities of nonlinear Bloch waves may be used to populate Floquet bands and measure their Chern number via the emergence of nontrivial polarization textures in a similar manner to static (undriven) lattices. Second, we show how the nonlinear dynamics of non-stationary superposition states may be used to identify dynamical symmetry inversion points in the intra-cycle dynamics, thereby allowing anomalous Floquet phases to be distinguished from the trivial phase. The approaches may be readily implemented using light propagation in nonlinear waveguide arrays.

physics.optics↗

arXiv2021

Higher-order topological phase induced by hybrid magneto-electric resonances

Rapid development of topological concepts in photonics unveils exotic phenomena such as unidirectional propagation of electromagnetic waves resilient to backscattering at sharp bends and disorder-immune localization of light at stable frequencies. Recently introduced higher-order topological insulators (HOTIs) bring in additional degrees of control over light confinement and steering. However, designs of photonic HOTIs reported so far are solely exploiting lattice geometries which are hard to reconfigure thus limiting tunability. Here, we elaborate a conceptually new mechanism to engineer higher-order topological phases which relies on the dual nature of electromagnetic field and exploits both electric and magnetic responses of the meta-atoms. Hybridization between these responses gives rise to the difference in the effective coupling which is controlled by the meta-atoms mutual orientations. This feature facilitates us to tailor photonic band topology exclusively via particle alignment and to flexibly reconfigure the topological phase. Focusing on the kagome array of split-ring resonators, we experimentally demonstrate topological edge and corner states in the microwave domain. Our findings provide a new promising route to induce and control higher-order topological phases and states.

cond-mat.mes-hall↗

arXiv2021

Gradient catastrophe of nonlinear photonic valley-Hall edge pulses

We derive nonlinear wave equations describing the propagation of slowly-varying wavepackets formed by topological valley-Hall edge states. We show that edge pulses break up even in the absence of spatial dispersion due to nonlinear self-steepening. Self-steepening leads to the previously-unattended effect of a gradient catastrophe, which develops in a finite time determined by the ratio between the pulse's nonlinear frequency shift and the size of the topological band gap. Taking the weak spatial dispersion into account results then in the formation of stable edge quasi-solitons. Our findings are generic to systems governed by Dirac-like Hamiltonians and validated by numerical modeling of pulse propagation along a valley-Hall domain wall in staggered honeycomb waveguide lattices with Kerr nonlinearity.

physics.optics↗

arXiv2021

Probing band topology using modulational instability

We analyze the modulational instability of nonlinear Bloch waves in topological photonic lattices. In the initial phase of the instability development captured by the linear stability analysis, long wavelength instabilities and bifurcations of the nonlinear Bloch waves are sensitive to topological band inversions. At longer timescales, nonlinear wave mixing induces spreading of energy through the entire band and spontaneous creation of wave polarization singularities determined by the band Chern number. Our analytical and numerical results establish modulational instability as a tool to probe bulk topological invariants and create topologically non-trivial wave fields.

physics.optics↗

arXiv2020

Nonlocal response of Mie-resonant dielectric particles

Mie-resonant high-index dielectric particles are at the core of modern all-dielectric photonics. In many situations, their response to the external fields is well-captured by the dipole model which neglects the excitation of higher-order multipoles. In that case, it is commonly assumed that the dipole moments induced by the external fields are given by the product of particle polarizability tensor and the field in the particle center. Here, we demonstrate that the dipole response of non-spherical subwavelength dielectric particles is significantly more complex since the dipole moments are defined not only by the field in the particle center but also by the second-order spatial derivatives of the field. As we prove, such nonlocal response is especially pronounced in the vicinity of anapole minimum in the scattering cross-section. We examine the excitation of high-index dielectric disk in microwave domain and silicon nanodisk in near infrared applying group-theoretical analysis and retrieving the nonlocal corrections to the dipole moments. Extending the discrete dipole model to include nonlocality of the dipole response, we demonstrate an improved agreement with full-wave numerical simulations. These results provide important insights into meta-optics of Mie-resonant non-spherical particles as well as metamaterials and metadevices based on them.

physics.optics↗

arXiv2020

Probing bulk topological invariants using leaky photonic lattices

Topological invariants characterising filled Bloch bands attract enormous interest, underpinning electronic topological insulators and analogous artificial lattices for Bose-Einstein condensates, photons, and acoustic waves. In the latter bosonic systems there is no Fermi exclusion principle to enforce uniform band filling, which makes measurement of their bulk topological invariants challenging. Here we show how to achieve controllable filling of bosonic bands using leaky photonic lattices. Leaky photonic lattices host transitions between bound and radiative modes at a critical energy, which plays a role analogous to the electronic Fermi level. Tuning this effective Fermi level into a band gap results in disorder-robust dynamical quantization of bulk topological invariants such as the Chern number. Our findings establish leaky lattices as a novel and highly flexible platform for exploring topological and non-Hermitian wave physics.

physics.optics↗

arXiv2020

Enhanced Light-Matter Interactions in Dielectric Nanostructures via Machine Learning Approach

A key concept underlying the specific functionalities of metasurfaces, i.e. arrays of subwavelength nanoparticles, is the use of constituent components to shape the wavefront of the light, on-demand. Metasurfaces are versatile and novel platforms to manipulate the scattering, colour, phase or the intensity of the light. Currently, one of the typical approaches for designing a metasurface is to optimize one or two variables, among a vast number of fixed parameters, such as various materials' properties and coupling effects, as well as the geometrical parameters. Ideally, it would require a multi-dimensional space optimization through direct numerical simulations. Recently, an alternative approach became quite popular allowing to reduce the computational cost significantly based on a deep-learning-assisted method. In this paper, we utilize a deep-learning approach for obtaining high-quality factor (high-Q) resonances with desired characteristics, such as linewidth, amplitude and spectral position. We exploit such high-Q resonances for the enhanced light-matter interaction in nonlinear optical metasurfaces and optomechanical vibrations, simultaneously. We demonstrate that optimized metasurfaces lead up to 400+ folds enhancement of the third harmonic generation (THG); at the same time, they also contribute to 100+ folds enhancement in optomechanical vibrations. This approach can be further used to realize structures with unconventional scattering responses.

physics.optics↗

arXiv2019

Photonic topological states mediated by staggered bianisotropy

Photonic topological structures supporting spin-momentum locked topological states underpin a plethora of prospects and applications for disorder-robust routing of light. One of the cornerstone ideas to realize such states is to exploit uniform bianisotropic response in periodic structures with appropriate lattice symmetries, which together enable the topological bandgaps. Here, it is demonstrated that staggered bianisotropic response gives rise to the topological states even in a simple lattice geometry whose counterpart with uniform bianisotropy is topologically trivial. The reason behind this intriguing behavior is in the difference of the effective coupling between the resonant elements with the same and with the opposite signs of bianisotropy. Based on this insight, a one-dimensional equidistant array is designed, which consists of high-index all-dielectric particles with alternating signs of bianisotropic response. The array possesses chiral symmetry and hosts topologically protected edge states pinned to the frequencies of hybrid magneto-electric modes. These results pave a way towards flexible engineering of topologically robust light localization and propagation by encoding spatially varying bianisotropy patterns in photonic structures.

physics.optics↗

arXiv2019

Spontaneous photon-pair generation at the nanoscale

Optical nanoantennas have shown a great capacity for efficient extraction of photons from the near to the far-field, enabling directional emission from nanoscale single-photon sources. However, their potential for the generation and extraction of multi-photon quantum states remains unexplored. Here we demonstrate experimentally the nanoscale generation of two-photon quantum states at telecommunication wavelengths based on spontaneous parametric down-conversion in an optical nanoantenna. The antenna is a crystalline AlGaAs nanocylinder, possessing Mie-type resonances at both the pump and the bi-photon wavelengths and when excited by a pump beam generates photonpairs with a rate of 35 Hz. Normalized to the pump energy stored by the nanoantenna, this rate corresponds to 1.4 GHz/Wm, being one order of magnitude higher than conventional on-chip or bulk photon-pair sources. Our experiments open the way for multiplexing several antennas for coherent generation of multi-photon quantum states with complex spatial-mode entanglement and applications in free-space quantum communications and sensing.

quant-ph↗

arXiv2019

Parity anomaly laser

We propose a novel supersymmetry-inspired scheme for achieving robust single mode lasing in arrays of coupled microcavities, based on factorizing a given array Hamiltonian into its "supercharge" partner array. Pumping a single sublattice of the partner array preferentially induces lasing of an unpaired zero mode. A chiral symmetry protects the zero mode similar to 1D topological arrays, but it need not be localized to domain walls or edges. We demonstrate single mode lasing over a wider parameter regime by designing the zero mode to have a uniform intensity profile.

physics.optics↗