arXiv subjects

Dmitry N. Chigrin

Publications and source records attributed to Dmitry N. Chigrin.

At least 19 recordsLinked to original sources

arXiv2026

Understanding inhomogeneous crystallization dynamics of phase-change materials in the vicinity of metallic nanoantennas

Optical metasurfaces composed of metallic or dielectric scatterers (meta-atoms) promise a powerful way of tailoring light-matter interactions. Phase-change materials (PCMs) are prime candidates for non-volatile resonance tuning of metasurfaces based on a refractive index change. Precise resonance control can be achieved by locally applying laser pulses to crystallize a PCM, modifying the dielectric surrounding of meta-atoms. However, the complex crystallization kinetics of PCMs in the vicinity of metallic meta-atoms have not been studied yet. Here, we experimentally investigate metallic dimer antennas on top of the PCM Ge3Sb2Te6 and address these nanoantennas with laser pulses. Our study reveals inhomogeneous crystallization caused by the absorption and heat conduction of the metallic nanoantennas. A self-consistent multiphysics model, including electromagnetic, thermal, and phase-transition processes, is employed to simulate the crystallization and understand the resulting resonance shift of the antennas. This model enables the optimization of the laser parameters and the geometry of the meta-atoms to achieve an optimal crystallization pattern and resonance shift. Our work paves the way towards complex antenna geometries optimized for local addressing of PCMs to achieve sophisticated crystallization patterns, enabling on-demand programming of individual nanoantennas within metasurfaces.

physics.optics↗

arXiv2022

Layer-Resolved Resonance Intensity of Evanescent Polariton Modes in Anisotropic Multilayers

Phonon polariton modes in layered anisotropic heterostructures are a key building block for modern nanophotonic technologies. The light-matter interaction for evanescent excitation of such a multilayer system can be theoretically described by a transfer matrix formalism. This method allows to compute the imaginary part of the p-polarized reflection coefficient Im$(r_{pp})$, which is typically used to analyze the polariton dispersion of the multilayer structure, but lacks the possibility to access the layer-resolved polaritonic response. We present an approach to compute the layer-resolved polariton resonance intensity in aribtrarily anisotropic layered heterostructures, based on calculating the Poynting vector extracted from a transfer matrix formalism. Our approach is independent of the experimental excitation conditions, and fulfills an empirical conservation law. As a test ground, we study two state-of-the-art nanophotonic multilayer systems, covering strong coupling and tunable hyperbolic surface phonon polaritons in twisted \MoO~double layers. Providing a new level of insight into the polaritonic response, our method holds great potential for understanding, optimizing and predicting new forms of polariton heterostructures in the future.

physics.optics↗

arXiv2022

Self-Assembled Ligand-Capped Plasmonic Au Nanoparticle Films in the Kretschmann Configuration for Sensing of Volatile Organic Compounds

Films of close-packed Au nanoparticles are coupled electrodynamically through their collective plasmon resonances. This collective optical response results in enhanced light-matter interactions, which can be exploited in various applications. Here, we demonstrate their application in sensing volatile organic compounds, using methanol as a test-case. Ordered films over several cm2 were obtained by interfacial self-assembly of colloidal Au nanoparticles (~10 nm diameter) through controlled evaporation of the solvent. Even though isolated nanoparticles of this size are inherently non-scattering, when arranged in a close-packed film the plasmonic coupling results in a strong reflectance and absorbance. The in-situ tracking of vapor phase methanol concentration through UV-Vis transmission measurements of the nanoparticle film is first demonstrated. Next, in-situ ellipsometry of the self-assembled films in the Kretschmann (also known as ATR) configuration is shown to yield enhanced sensitivity, especially with phase difference measurements. Our study shows the excellent agreement between theoretical models of the spectral response of self-assembled films with experimental in-situ sensing experiments. At the same time, the theoretical framework provides the basis for the interpretation of the various observed experimental trends. Combining periodic nanoparticle films with ellipsometry in the Kretschmann configuration is a promising strategy towards highly sensitive and selective plasmonic thin-film devices based on colloidal fabrication methods for volatile organic compound (VOC) sensing applications.

physics.optics↗

arXiv2020

The Potential of Combining Thermal Scanning Probes and Phase-Change Materials for Tunable Metasurfaces

Metasurfaces allow for the spatiotemporal variation of amplitude, phase, and polarization of optical wavefronts. Implementation of active tunability of metasurfaces promises compact flat optics capable of reconfigurable wavefront shaping. Phase-change materials (PCMs), such as germanium telluride or germanium antimony telluride, are a prominent material class enabling reconfigurable metasurfaces due to their large refractive index change upon structural transition. However, commonly employed laser-induced switching of PCMs limits the achievable feature sizes and thus, restricts device miniaturization. Here, we propose thermal scanning-probe-induced local switching of germanium telluride to realize near-infrared metasurfaces with feature sizes far below what is achievable with diffraction-limited optical switching. Our design is based on a planar multilayer stack and does not require fabrication of protruding dielectric or metallic resonators as commonly applied in the literature. Instead, we numerically demonstrate that a broad-band tuning of perfect absorption could be realized by the localized and controlled tip-induced crystallization of the PCM layer. The spectral response of the metasurface is explained using simple resonance mode analysis and numerical simulations. To facilitate experimental realization, we provide a detailed theoretical description of the tip-induced crystallization employing multiphysics simulations to demonstrate the great potential for fabricating compact reconfigurable metasurfaces. Our concept allows for tunable perfect absorption and can be applied not only for thermal imaging or sensing, but also for spatial frequency filtering.

physics.app-ph↗

arXiv2014

Enhanced emission extraction and selective readout of NV centers with all-dielectric nanoantennas

We propose a novel approach to facilitate a readout processes of isolated negatively charged nitrogen-vacancy (NV) centers based on the concept of all-dielectric nanoantennas. We reveal that all-dielectric nanoantenna can significantly enhance both the emission rate and emission extraction efficiency of a photoluminescence signal from a single NV center in a diamond nanoparticle placed on a dielectric substrate. We prove that the proposed approach provides high directivity, large Purcell factor, and efficient beam steering, thus allowing an efficient far-field initialization and readout of several NV centers separated by subwavelength distances.

physics.optics↗

arXiv2012

Graphene hyperlens for terahertz radiation

We propose a graphene hyperlens for the terahertz (THz) range. We employ and numerically examine a structured graphene-dielectric multilayered stack that is an analogue of a metallic wire medium. As an example of the graphene hyperlens in action we demonstrate an imaging of two point sources separated with distance $λ_{0}/5$. An advantage of such a hyperlens as compared to a metallic one is the tunability of its properties by changing the chemical potential of graphene. We also propose a method to retrieve the hyperbolic dispersion, check the effective medium approximation and retrieve the effective permittivity tensor.

physics.optics↗

arXiv2011

Plasmonic nanoparticle monomers and dimers: From nano-antennas to chiral metamaterials

We review the basic physics behind light interaction with plasmonic nanoparticles. The theoretical foundations of light scattering on one metallic particle (a plasmonic monomer) and two interacting particles (a plasmonic dimer) are systematically investigated. Expressions for effective particle susceptibility (polarizability) are derived, and applications of these results to plasmonic nanoantennas are outlined. In the long-wavelength limit, the effective macroscopic parameters of an array of plasmonic dimers are calculated. These parameters are attributable to an effective medium corresponding to a dilute arrangement of nanoparticles, i.e., a metamaterial where plasmonic monomers or dimers have the function of "meta-atoms". It is shown that planar dimers consisting of rod-like particles generally possess elliptical dichroism and function as atoms for planar chiral metamaterials. The fabricational simplicity of the proposed rod-dimer geometry can be used in the design of more cost-effective chiral metamaterials in the optical domain.

physics.optics↗

arXiv2011

Efficient construction of maximally localized photonic Wannier functions: locality criterion and initial conditions

Wannier function expansions are well suited for the description of photonic- crystal-based defect structures, but constructing maximally localized Wannier functions by optimizing the phase degree of freedom of the Bloch modes is crucial for the efficiency of the approach. We systematically analyze different locality criteria for maximally localized Wannier functions in two- dimensional square and triangular lattice photonic crystals, employing (local) conjugate-gradient as well as (global) genetic-algorithm-based, stochastic methods. Besides the commonly used second moment (SM) locality measure, we introduce a new locality measure, namely the integrated modulus (IM) of the Wannier function. We show numerically that, in contrast to the SM criterion, the IM criterion leads to an optimization problem with a single extremum, thus allowing for fast and efficient construction of maximally localized Wannier functions using local optimization techniques. We also present an analytical formula for the initial choice of Bloch phases, which under certain conditions represents the global maximum of the IM criterion and, thus, further increases the optimization efficiency in the general case.

physics.optics↗

arXiv2011

Plasmonic rod dimers as elementary planar chiral meta-atoms

Electromagnetic response of metallic rod dimers is theoretically calculated for arbitrary planar arrangement of rods in the dimer. It is shown that dimers without an in-plane symmetry axis exhibit elliptical dichroism and act as "atoms" in planar chiral metamaterials. Due to a very simple geometry of the rod dimer, such planar metamaterials are much easier in fabrication than conventional split-ring or gammadion-type structures, and lend themselves to a simple analytical treatment based on coupled dipole model. Dependencies of metamaterial's directional asymmetry on the dimer's geometry are established analytically and confirmed in numerical simulations.

physics.optics↗

arXiv2011

Light Scattering on Nanowire Antennas: A Semi-Analytical Approach

Two semi-analytical approaches to solve the problem of light scattering on nanowire antennas are developed and compared. The derivation is based on the exact solution of the plane wave scattering problem in case of an infinite cylinder. The original three-dimensional problem is reduced in two alternative ways to a simple one-dimensional integral equation, which can be solved numerically by a method of moments approach. Scattering cross sections of gold nanowire antennas with different lengths and aspect ratios are analysed for the optical and near-infrared spectral range. Comparison of the proposed semi-analytical methods with the numerically rigorous discrete dipole approximation method demonstrates good agreement as well as superior numerical performance.

physics.optics↗

arXiv2009

Optical memory based on ultrafast wavelength switching in a bistable microlaser

We propose an optical memory cell based on ultrafast wavelength switching in coupled-cavity microlasers, featuring bistability between modes separated by several nanometers. A numerical implementation is demonstrated by simulating a two-dimensional photonic crystal microlaser. Switching times of less than 10 ps, switching energy around 15--30 fJ and on-off contrast of more than 40 dB are achieved. Theoretical guidelines for optimizing the performance of the memory cell in terms of switching time and energy are drawn.

physics.optics↗

arXiv2009

Spatial distribution of Cherenkov radiation in periodic dielectric media

The nontrivial dispersion relation of a periodic medium affects both the spectral and the spatial distribution of Cherenkov radiation. We present a theory of the spatial distribution of Cherenkov radiation in the far-field zone inside arbitrary three- and two-dimensional dielectric media. Simple analytical expressions for the far-field are obtained in terms of the Bloch mode expansion. Numerical examples of the Cherenkov radiation in a two-dimensional photonic crystal is presented. The developed analytical theory demonstrates good agreement with numerically rigorous finite-difference time-domain calculations.

physics.optics↗

arXiv2009

Bistability and mode interaction in microlasers

We investigate the possibility of bistable lasing in microcavity lasers as opposed to bulk lasers. To that end, the dynamic behavior of a microlaser featuring two coupled, interacting modes is analytically investigated within the framework of a semiclassical laser model, suitable for a wide range of cavity shapes and mode geometries. Closed-form coupled mode equations are obtained for all classes of laser dynamics. We show that bistable operation is possible in all of these classes. In the simplest case (class-A lasers) bistability is shown to result from an interplay between coherent (population-pulsation) and incoherent (hole-burning) processes of mode interaction. We find that microcavities offer better conditions to achieve bistable lasing than bulk cavities, especially if the modes are not degenerate in frequency. This results from better matching of the spatial intensity distribution of microcavity modes. In more complicated laser models (class-B and class-C) bistability is shown to persist for modes even further apart in frequency than in the class-A case. The predictions of the coupled mode theory have been confirmed using numerical finite-difference time-domain calculations.

physics.optics↗

arXiv2009

Theory of Cherenkov radiation in periodic dielectric media: Emission spectrum

The Cherenkov radiation is substantially modified in the presence of a medium with a nontrivial dispersion relation. We consider Cherenkov emission spectra of a point charge moving in general three- (3D) and two-dimensional (2D) photonic crystals. Exact analytical expressions for the spectral distribution of the radiated power are obtained in terms of the Bloch mode expansion. The resulting expression reduces to a simple contour integral (3D case) or a one-dimensional sum (2D case) over a small fraction of the reciprocal space, which is defined by the generalized Cherenkov condition. We apply our method to a specific case of an electron moving with different velocities in a 2D square-lattice photonic crystal. Our method demonstrates an excellent agreement with numerically rigorous finite-difference time-domain calculations while being less demanding on computational resources.

physics.optics↗

arXiv2008

Spatial distribution of the emission intensity in a photonic crystal: Self-interference of Bloch eigenwaves

The analysis of an angular distribution of the emission intensity of a two-level atom (dipole) in a photonic crystal reveals an enhancement of the emission rate in some observation directions. Such an enhancement is the result of the bunching of many Bloch eigenwaves with different wave vectors in the same direction due to the crystal anisotropy. If a spatial distribution of the emission intensity is considered, the interference of these eigenwaves should be taken into account. In this paper, the far-field emission pattern of a two-level atom is discussed in the framework of the asymptotic analysis the classical macroscopic Green function. Numerical example is given for a two-dimensional square lattice of air holes in polymer. The relevance of results for experimental observation is discussed.

physics.optics↗

arXiv2007

Coupled nanopillar waveguides: optical properties and applications

In this paper we review basic properties of coupled periodic and aperiodic nanopillar waveguides. A coupled nanopillar waveguide consists of several rows of periodically or aperiodically placed dielectric rods (pillars). In such a waveguide, light confinement is due to the total internal reflection, while guided modes dispersion is strongly affected by the waveguide structure. We present a systematic analysis of the optical properties of coupled nanopillar waveguides and discuss their possible applications for integrated optics.

physics.optics↗

arXiv2007

Switchable lasing in coupled multimode microcavities

We propose the new concept of a switchable multimode microlaser. As a generic, realistic model of a multimode microresonator a system of two coupled defects in a two-dimensional photonic crystal is considered. We demonstrate theoretically that lasing of the cavity into one selected resonator mode can be caused by injecting an appropriate optical pulse at the onset of laser action (injection seeding). Temporal mode-to-mode switching by re-seeding the cavity after a short cool-down period is demonstrated by direct numerical solution. A qualitative analytical explanation of the mode switching in terms of the laser bistability is presented.

cond-mat.mes-hall↗

arXiv2006

Low-loss resonant modes in deterministically aperiodic nanopillar waveguides

Quasiperiodic Fibonacci-like and fractal Cantor-like single- and multiple-row nanopillar waveguides are investigated theoretically employing the finite difference time domain (FDTD) method. It is shown that resonant modes of the Fibonacci and Cantor waveguides can have a Q-factor comparable with that of a point-defect resonator embedded in a periodic nanopillar waveguide, while the radiation is preferably emitted into the waveguide direction, thus improving coupling to an unstructured dielectric waveguide located along the structure axis. This is especially so when the dielectric waveguide introduces a small perturbation in the aperiodic structure, breaking the structure symmetry while staying well apart from the main localization area of the resonant mode. The high Q-factor and increased coupling with external dielectric waveguide suggest using the proposed deterministically aperiodic nanopillar waveguides in photonic integrated circuits.

cond-mat.mtrl-sci↗