arXiv subjects

Pavel Ginzburg

Publications and source records attributed to Pavel Ginzburg.

At least 37 records · Page 2Linked to original sources

arXiv2023

Dual-band electro-optically steerable antenna

The ability to obtain dynamic control over an antenna radiation pattern is one of the main functions, desired in a vast range of applications, including wireless communications, radars, and many others. Widely used approaches include mechanical scanning with antenna apertures and phase switching in arrays. Both of those realizations have severe limitations, related to scanning speeds and implementation costs. Here we demonstrate a solution, where the antenna pattern is switched with optical signals. The system encompasses an active element, surrounded by a set of cylindrically arranged passive dipolar directors, functionalized with tunable impedances. The control circuit is realized as a bipolar transistor, driven by a photodiode. Light illumination in this case serves as a trigger, capable of either closing or opening the transistor, switching the impedance between two values. Following this approach, a compact half-a-wavelength footprint antenna, capable to switch between 6 dBi directional patterns within a few milliseconds latency was demonstrated. The developed light activation approach allows constructing devices with multiple almost non-interacting degrees of freedom, as brunched feeding network is not required. The capability of MHz and faster switching between multiple electromagnetic degrees of freedom open pathways to new wireless applications, where fast beam steering and beamforming performances are required.

physics.app-ph↗

arXiv2022

Surpassing super-radiant scattering limit in a flat split-ring resonator

Electromagnetic scattering bounds on subwavelength structures play an important role in estimating performances of antennas, RFID tags, and other wireless communication devices. An appealing approach to increase a scattering cross-section is accommodating several spectrally overlapping resonances within a structure. However, numerous fundamental and practical restrictions have been found and led to the formulation of Chu-Harrington, Geyi, and other limits, which provide an upper bound to scattering efficiencies. Here we introduce a 2D array of near-field coupled split-ring resonators and optimize its scattering performances with the aid of a genetic algorithm, operating in 19th-dimensional space. Experimental realization of the device is demonstrated to surpass the theoretical single-channel limit by a factor of >2, motivating the development of tighter bounds of scattering performances. A super-radiant criterion is suggested to compare maximal scattering cross-sections versus the single-channel dipolar limit multiplied by the number of elements within the array. This new empirical criterion, which aims on addressing performances of subwavelength arrays formed by near-field coupled elements, was found to be rather accurate in application to the superscatterer, reported here. Furthermore, the super-radiant bound was empirically verified with a Monte-Carlo simulation, collecting statistics on scattering cross sections of a large set of randomly distributed dipoles. The demonstrated flat superscatterer can find use as a passive electromagnetic beacon, making miniature airborne and terrestrial targets to be radar visible.

physics.app-ph↗

arXiv2021

Golden Vaterite as a Mesoscopic Metamaterial for Biophotonic Applications

Mesoscopic photonic systems with tailored optical responses have great potential to open new frontiers in implantable biomedical devices. However, biocompatibility is typically a problem, as engineering of optical properties often calls for using toxic compounds and chemicals, unsuitable for in vivo applications. Here, we demonstrate a unique approach to biofriendly delivery of optical resonances. We show that the controllable infusion of gold nanoseeds into polycrystalline submicron vaterite spherulites gives rise to a variety of electric and magnetic Mie resonances, producing a tuneable mesoscopic optical metamaterial. The three-dimensional reconstruction of the spherulites demonstrates the capability of controllable gold loading with volumetric filling factors exceeding 28%. Owing to the biocompatibility of the constitutive elements, golden vaterite paves the way to introduce designer-made Mie resonances to cuttingedge biophotonic applications. We exemplify this concept by showing efficient laser heating of gold-filled vaterite spherulites at red and near-infrared wavelengths, highly desirable in photothermal therapy and photoacoustic tomography

physics.optics↗

arXiv2021

Biological Kerker effect boosts light collection efficiency in plants

Being the polymorphs of calcium carbonate (CaCO3), vaterite and calcite have attracted a great deal of attention as promising biomaterials for drug delivery and tissue engineering applications. Furthermore, they are important biogenic minerals, enabling living organisms to reach specific functions. In nature, vaterite and calcite monocrystals typically form self-assembled polycrystal micro- and nanoparticles, also referred to as spherulites. Here, we demonstrate that alpine plants belonging to the Saxifraga genus can tailor light scattering channels and utilize multipole interference effect to improve light collection efficiency via producing CaCO3 polycrystal nanoparticles on the margins of their leaves. To provide a clear physical background behind this concept, we study optical properties of artificially synthesized vaterite nanospherulites and reveal the phenomenon of directional light scattering. Darkfield spectroscopy measurements are supported by a comprehensive numerical analysis, accounting for the complex microstructure of particles. We demonstrate the appearance of generalized Kerker condition, where several higher order multipoles interfere constructively in the forward direction, governing the interaction phenomenon. As a result, highly directive forward light scattering from vaterite nanospherulites is observed in the entire visible range. Furthermore, ex vivo studies of microstructure and optical properties of leaves for the alpine plants Saxifraga 'Southside Seedling' and Saxifraga Paniculata Ria are performed and underlined the importance of Kerker effect for these living organisms. Our results pave the way for a bioinspired strategy of efficient light collection by selfassembled polycrystal CaCO3 nanoparticles via tailoring light propagation directly to the photosynthetic tissue with minimal losses to undesired scattering channels.

physics.bio-ph↗

arXiv2021

Broadband resonant calibration-free complex permittivity retrieval of liquid solutions

Material susceptibilities govern interactions between electromagnetic waves and matter and are of a crucial importance for basic understanding of natural phenomena and for tailoring practical applications. Here we present a new calibration-free method for relative complex permittivity retrieval, which allows using accessible and cheap apparatus and simplifies the measurement process. The method combines advantages of resonant and non-resonant techniques, allowing to extract parameters of liquids and solids in a broad frequency range, where material's loss tangent is less than 0.5. The essence of the method is based on exciting magnetic dipole resonance in a spherical sample with variable dimensions. Size-dependent resonant frequencies and quality factors of magnetic dipolar modes are mapped on real and imaginary parts of permittivity by employing Mie theory. Samples are comprised of liquid solutions, enclosed in stretchable covers, which allows changing the dimensions continuously. This approach allows tuning magnetic dipolar resonance over a wide frequency range, effectively making resonance retrieval method broadband. The technique can be extended to powder and solid materials, depending on their physical parameters, such as granularity and processability.

physics.app-ph↗

arXiv2021

Controllable synthesis of calcium carbonate with different geometry: comprehensive analysis of particles formation, their cellular uptake and biocompatibility

Carefully designed micro and nanocarriers can provide significant advantages over conventional macroscopic counterparts in biomedical applications. The set of requirements including a high loading capacity, triggered release mechanisms, biocompatibility, and biodegradability should be considered for the successful delivery realization. Porous calcium carbonate (CaCO3) is one of the most promising platforms, which can encompass all the beforehand mentioned requirements. Here, we study both the particles formation and biological applicability of CaCO3. In particular, anisotropic differently shaped CaCO3 particles were synthesized using green sustainable approach based on co-precipitation of calcium chloride and sodium carbonate/bicarbonate at different ratios in the presence of organic additives. The impact of salts concentrations, reaction time, as well as organic additives was systematically researched to achieve controllable and reliable design of CaCO3 particles. It has been demonstrated that the crystallinity (vaterite or calcite phase) of particles depends on the initial salts concentrations. The loading capacity of prepared CaCO3 particles is determined by their surface properties such as specific surface area, pore size and zeta-potential. Differently shaped CaCO3 particles (spheroids, ellipsoids, toroids) were used to evaluate their uptake efficiency on the example of C6 glioma cells. The results show that the ellipsoidal particles possess a higher probability for internalization by cancer cells. All tested particles were also found to have a good biocompatibility. The capability to design physicochemical properties of CaCO3 particles has a significant impact on drug delivery applications, since the particles geometry substantially affects cell behavior (internalization, toxicity) and allows outperforming standard spherical counterparts.

cond-mat.soft↗

arXiv2021

Auxiliary Optomechanical Tools for 3D Cell Manipulation

Advances in laser and optoelectronic technologies brought the general concept of optomechanical manipulation to the level of standard biophysical tools, paving ways towards controlled experiments and measurements of tiny mechanical forces. Recent developments in direct laser writing (DLW), enabled the realization of new types of micron-scale optomechanical tools, capable of performing designated functions. Here we further develop the concept of DLW-fabricated optomechanically-driven tools and demonstrate full-3D manipulation capabilities over biological objects. In particular, we resolved a long-standing problem of out-of-plane rotation in a pure liquid, which was demonstrated on a living cell, clamped between a pair of forks, designed for efficient manipulation with holographic optical tweezers. The demonstrated concept paves new ways towards realization of flexible tools for performing on-demand functions over biological objects, such as cell tomography and surgery to name just few.

physics.optics↗

arXiv2021

Partially Coherent Radar Unties Range Resolution from Bandwidth Limitations

It is widely believed that range resolution, the ability to distinguish between two closely situated targets, depends inversely on the bandwidth of the transmitted radar signal. Here we demonstrate a different type of ranging system, which possesses superior range resolution that is almost completely free of bandwidth limitations. By sweeping over the coherence length of the transmitted signal, the partially coherent radar experimentally demonstrates an improvement of over an order of magnitude in resolving targets, compared to standard coherent radars with the same bandwidth.. A theoretical framework is developed to show that the resolution could be further improved without a bound, revealing a tradeoff between bandwidth and sweep time. This concept offers solutions to problems which require high range resolution and accuracy but available bandwidth is limited, as is the case for the autonomous car industry, optical imaging, and astronomy to name just few.

eess.SP↗

arXiv2021

Nonlinear Nanophotonic Circuitry: Tristable and Astable Multivibrators and Chaos Generator

The concept of lumped optical nanoelements (or metactronics), wherein nanometer-scale structures act as nanoinductors, nanocapacitors and nanoresistors, has attracted a great deal of attention as a simple toolbox for engineering different nanophotonic devices in analogy with microelectronics. While recent studies of the topic have been predominantly focused on linear functionalities, nonlinear dynamics in microelectronic devices plays a crucial role and provides a majority of functions, employed in modern applications. Here, we extend the metactronics paradigm and add nonlinear dynamical modalities to those nanophotonic devices that have never been associated with optical nanoantennas. Specifically, we show that nonlinear dimer nanoantennae can operate in the regimes of tristable and astable multivibrators as well as chaos generators. The physical mechanism behind these modalities relies on the Kerr-type nonlinearity of nanoparticles in the dimer enhanced by a dipolar localized surface plasmon resonance. This allows one to provide a positive nonlinear feedback at moderate optical intensities, leading to the desired dynamical behavior via tuning the driving field parameters. Our findings shed light on a novel class of nonlinear nanophotonic devices with a tunable nonlinear dynamical response.

physics.optics↗

arXiv2021

Experimental observation of intrinsic light localization in photonic icosahedral quasicrystals

One of the most intriguing problems of light transport in solids is the localization that has been observed in various disordered photonic structures1-11. The light localization in defect-free icosahedral quasicrystals has recently been predicted theoretically without experimental verification10. Here we report on the fabrication of submicron-size dielectric icosahedral quasicrystals and demonstrate the results of detailed studies of the photonic properties of these structures. Here, we present the first direct experimental observation of intrinsic light localization in defect-free quasicrystals. This result was obtained in time-resolved measurements at different laser wavelengths in the visible. We linked localization with the aperiodicity of the icosahedral structure, which led to uncompensated scattering of light from an individual structural element over the entire sphere, providing multiple scattering inside the sample and, as a result, the intrinsic localization of light.

physics.optics↗

arXiv2021

4D Optically Reconfigurable Volumetric Metamaterials

Metamaterials are artificially created media, which allow introducing additional degrees of freedom into electromagnetic design by controlling constitutive material parameters. Reconfigurable time-dependent metamaterials can further enlarge those capabilities by introducing a temporal variable as an additional controllable parameter. Here we demonstrate a first-of-its-kind reconfigurable volumetric metamaterial-based scatterer, wherein the electromagnetic properties are controlled dynamically with light. In particular, hybridized resonances in arrays of split ring resonators give rise to a collective mode that presents properties of artificial high-frequency magnetism for centimeter waves. Resonant behavior of each individual ring is controlled with a photocurrent, which allows the fast tuning of macroscopic effective permeability. Thus, the artificial gigahertz magnon resonant excitation within a subwavelength spherical scatterer is governed by light intensity. Four-dimensional control over electromagnetic scattering in both space and time opens new venues for modern applications, including wireless communications and automotive radars to name just a few.

physics.optics↗

arXiv2021

Fast computation of scattered fields with arbitrary beam scattering

Electromagnetic scattering on a sphere is one of the most fundamental problems, which has a closed form analytical solution in the form of Mie series. Being initially formulated for a plane incident wave, the formalism can be extended to more complex forms of incident illumination. Here we present a fast calculation approach to address the scattering problem in the case of arbitrary illumination, incident on a spherical scatterer. This method is based on the plane wave decomposition of the incident illumination and weighted integration of Mie solutions, rotated to a global coordinate system. Tabulated solutions, sampled with an accurately level of sparsity, and efficient rotational transformations allow performing fast calculations on electrically large structures, outperforming capabilities relatively to other numerical techniques. Our approach is suitable for real-time analysis of electromagnetic scattering from electrically large objects, which is essential for monitoring and control applications, such as optomechanical manipulation, scanning microscope, and fast optimization algorithms.

physics.optics↗

arXiv2021

Coupled Micro-Doppler Signatures of Closely Located Targets

The classical Doppler shift originates from the movement of a target's center of mass, but it does not hold information about the internal dynamics of the scattering object. In contrast, micro-Doppler signatures contain data about the micro-motions that arise from internal degrees of freedom within the target (such as rotation and vibration), which can be remotely detected by careful analysis of the scattered field. Here we investigate, both theoretically and experimentally, how coupling between a pair of closely situated targets affects the resulting micro-Doppler signatures. The presented model considers a pair of near-field coupled resonators with dynamically reconfigurable scattering properties. Voltage controlled varactor diodes enable modulating the scattering cross-section of each target independently, mimicking rotational degrees of freedom. As a result, coupled micro-Doppler combs are observed, containing new frequency components that arise from the near field coupling, making it possible to extract information about the internal geometry of the system from far-field measurements. From a practical point of view, micro-Doppler spectroscopy allows remote classification of distant objects, while deep understanding of the coupling effects on such signatures in the low frequency regime can provide valuable insight for radar and sonar systems, as well as optical and stellar radio-interferometry, among many others.

physics.app-ph↗

arXiv2021

Broadband Radar Invisibility with Time-Dependent Metasurfaces

Concealing objects from interrogation has been a primary objective since the integration of radars into surveillance systems. Metamaterial-based invisibility cloaking, which was considered a promising solution, did not yet succeed in delivering reliable performance against real radar systems, mainly due to its narrow operational bandwidth. Here we propose an approach, which addresses the issue from a signal-processing standpoint and, as a result, is capable of coping with the vast majority of unclassified radar systems by exploiting vulnerabilities in their design. In particular, we demonstrate complete concealment of a 0.25 square meter moving metal plate from an investigating radar system, operating in a broad frequency range approaching 20% bandwidth around the carrier of 1.5GHz. The key element of the radar countermeasure is a temporally modulated coating. This auxiliary structure is designed to dynamically and controllably adjust the reflected phase of the impinging radar signal, which acquires a user-defined Doppler shift. A special case of interest is imposing a frequency shift that compensates for the real Doppler signatures originating from the motion of the target. In this case the radar will consider the target static, even though it is moving. As a result, the reflected echo will be discarded by the clutter removal filter, which is an inherent part of any modern radar system that is designed to operate in real conditions. This signal-processing loophole allows rendering the target invisible to the radar even though it scatters electromagnetic radiation. This application claims the benefit of patent number 273995, filed on April 16 2020.

eess.SP↗

arXiv2021

Multipole Engineering of Attractive-Repulsive and Bending Optical Forces

Focused laser beams allow controlling mechanical motion of objects and can serve as a tool for assembling complex micro and nano structures in space. While in a vast majority of cases small particles experience attractive gradient forces and repulsive radiation pressure, introduction of additional degrees of freedom into optomechanical manipulation suggests approaching new capabilities. Here we analyze optical forces acting on a high refractive index silicon sphere in a focused Gaussian beam and reveal new regimes of particles anti-trapping. Multipolar analysis allows separating an optical force into interception and recoil components, which have a completely different physical nature resulting in different mechanical actions. In particular, interplaying interception radial forces and multipolar resonances within a particle can lead to either trapping or anti-trapping scenarios, depending of the overall system parameters. At the same time, the recoil force generates a significant azimuthal component along with an angular-dependent radial force. Those contribution enable enhancing either trapping or anti-trapping regimes and also introduce bending reactions. These effects are linked to the far-field multipole interference resulting and, specifically, to its asymmetric scattering diagrams. The later approach is extremely useful, as it allows assessing the nature of optomechanical motion by observing far-field patterns. Multipolar engineering of optical forces, being quite general approach, is not necessarily linked to simple spherical shapes and paves a way to new possibilities in microfluidic applications, including sorting and micro assembly of nontrivial volumetric geometries.

physics.optics↗

arXiv2020

Efficient radiational outcoupling of electromagnetic energy from hyperbolic metamaterial resonators

Hyperbolic metamaterials were initially proposed in optics to boost radiation efficiencies of quantum emitters. Adopting this concept for antenna design can allow approaching long-standing challenges in radio physics. For example, impedance matching and gain are among the most challenging antenna parameters to achieve in case when a broadband operation is needed. Here we pro-pose and numerically analyse a new compact antenna design, based on hyperbolic metamaterial slab with a patterned layer on top. Energy from a subwavelength loop antenna is shown to be efficiently harvested into bulk modes of the metamaterial over a broad frequency range. Highly localized propagating waves within the medium have a well-resolved spatial-temporal separation owing to the hyperbolic type of effective permeability tensor. This strong interplay between chromatic and modal dispersions enables routing different frequencies into different spatial locations within compact subwavelength geometry. An array of non-overlapping resonant elements is placed on the metamaterial layer and provides a superior matching of localized electromagnetic energy to the free space radiation. As the result, two-order of magnitude improvement in linear gain of the device is predicted. The proposed new architecture can find a use in applications, where multiband or broadband compact devices are required.

physics.app-ph↗

arXiv2020

Multipole engineering for enhanced backscattering modulation

An efficient modulation of backscattered energy is one of the key requirements for enabling efficient wireless communication channels. Typical architectures, being based on either electronically or mechanically modulated reflectors, cannot be downscaled to subwavelengths dimensions by design. Here we show that integrating high-index dielectric materials with tunable subwavelength resonators allows achieving an efficient backscattering modulation, keeping a footprint of an entire structure small. An interference between high-order Mie resonances leads to either enhancement or suppression of the backscattering, depending on a control parameter. In particular, a ceramic core-shell, driven by an electronically tunable split ring resonator was shown to provide a backscattering modulation depth as high as tens of the geometrical cross-section of the structure. The design was optimized towards maximizing reading range of radio frequency identification (RFID) tags and shown to outperform existing commercial solutions by orders of magnitude in terms of the modulation efficiency. The proposed concept of multipole engineering allows one to design a new generation of miniature beacons and modulators for wireless communication needs and other relevant applications.

physics.app-ph↗

arXiv2020

Wire Resonator as a Broadband Huygens Superscatterer

Interference phenomena render tailoring propagation of electromagnetic waves by controlling phases of several scattering channels. Huygens element, being a representative example of this approach, allows enhancement of the scattering from an object in a forward direction, while the reflection is suppressed. However, a typical resonant realization of Huygens element employs constructive interference between electric and magnetic dipolar resonances that makes it relatively narrowband. Here we develop the concept of a broadband resonant Huygens element, based on a circular array of vertically aligned metal wires. Accurate management of multipole interference in an electrically small structure results in directional scattering over a large bandwidth, acceding 10% of the carrier frequency. Being constructed from non-magnetic materials, this structure demonstrates a strong magnetic response appearing in dominating magnetic multipoles over electric counterparts. Moreover, we predict and observe very high-order magnetic hexadecapole (M16-pole) and magnetic triakontadipole (M32-pole) with quality factors, approaching 6,000. The experimental demonstration is performed at the low GHz spectral range. Our findings shed light on a simple approach for engineering compact and open electromagnetic devices (antennas, directional reflectors, refractors, etc.) able to tailor wave propagation in a broadband domain, concentrate strong magnetic field, and generate high-order magnetic multipoles.

physics.app-ph↗