arXiv subjects

V. I. Belotelov

Publications and source records attributed to V. I. Belotelov.

At least 37 records · Page 2Linked to original sources

arXiv2021

One-dimensional optomagnonic microcavities for selective excitation of perpendicular standing spin waves

Here we propose a method of the excitation of perpendicular standing spin waves (PSSWs) of different orders in an optomagnonic microcavity by ultrashort laser pulses. The microcavity is formed by a magnetic dielectric film surrounded by dielectric non-magnetic Bragg mirrors. Optical cavity modes in the magnetic layer provide concentration and strongly non-uniform distribution of the optical power over the layer thickness and therefore induce the effective field of the inverse Faraday effect also spatially non-uniform. It results in excitation of PSSWs. PSSWs whose wavevector is closest to the wavevector characterizing distribution of the inverse Faraday effect field are excited most efficiently. Consequently, a key advantage of this approach is a selectivity of the PSSW excitation which allows to launch PSSWs of required orders only. All-optical operation of the optomagnonic cavities opens new possibilities for their applications for quantum technologies.

physics.optics↗

arXiv2020

Nanophotonic structures with optical surface modes for tunable spin current generation

Heat generated by spin currents in spintronics-based devices is typically much less than that generated by charge current flows in conventional electronic devices. However, the conventional approaches for excitation of spin currents based on spin-pumping and spin Hall effect are limited in efficiency which restricts their application for viable spintronic devices. We propose a novel type of photonic-crystal (PC) based structures for efficient and tunable optically-induced spin current generation via the Spin Seebeck and inverse spin Hall effects. It is experimentally demonstrated that optical surface modes localized at the PC surface covered by ferromagnetic layer and materials with giant spin-orbit coupling (SOC) notably increase the efficiency of the optically-induced spin current generation and provides its tunability by modifying light wavelength or angle of incidence. Up to 100% of the incident light power can be transferred to heat within the SOC layer and, therefore, to spin current. Importantly, high efficiency becomes accessible even for ultra-thin SOC layers. Moreover, surface patterning of the PC-based spintronic nanostructure allows local generation of spin currents at the pattern scales rather than diameter of the laser beam.

cond-mat.mes-hall↗

arXiv2020

Layer-Selective Magnetization Switching in the Chirped Photonic Crystal with GdFeCo

Here we propose a magnetophotonic structure for the layer-selective magnetization switching with ultrashort laser pulses of different wavelengths. It is based on a chirped magnetophotonic crystal (MPC) containing magnetic GdFeCo and nonmagnetic dielectric layers. At each operating wavelength the laser pulses heat up to necessary level only one GdFeCo layer that leads to its magnetization reversal without any impact on the magnetization of the other layers. Moreover, magneto-optical reading of the MPC magnetization state is discussed. Lateral dimensions of the considered MPC can be made small enough to operate as a unit cell for data storage.

physics.optics↗

arXiv2020

Bose condensation and spin superfluidity of magnons in a perpendicularly magnetized film of yttrium iron garnet

The formation of a Bose condensate of magnons in a perpendicularly magnetized film of yttrium iron garnet under radio-frequency pumping in a strip line is studied experimentally. The characteristics of nonlinear magnetic resonance and the spatial distribution of the Bose condensate of magnons in the magnetic field gradient are investigated. In these experiments, the Bosonic system of magnons behaves similarly to the Bose condensate of magnons in the antiferromagnetic superfluid 3He-B, which was studied in detail earlier. Magnonic BEC forms a coherently precessing state with the properties of magnonic superfluidity. Its stability is determined by the repulsive potential between excited magnons, which compensates for the inhomogeneity of the magnetic field.

cond-mat.mes-hall↗

arXiv2020

Vector magneto-optical magnetometer based on the resonant all-dielectric gratings with highly anisotropic iron-garnet films

A sensitive vector magnetometry with high spatial resolution is important for various practical applications, such as magnetocardiography, magnetoencephalography, explosive materials detection and many others. We propose a magnetometer based on the magnetic iron-garnet film possessing a very high magnetic anisotropy, placed in the rotating external magnetic field. Each of the measured magnetic field spatial components produces different temporal harmonics in the out-of-plane magnetization dependence. The dielectric resonant grating placed on the top of an ultrathin film enhanced the magneto-optical response 10 times which makes it possible to achieve 10 times higher spatial resolution in the perpendicular to the film direction. The reported magneto-optical magnetometer allows one to measure simultaneously all three spatial components of the magnetic field with high spatial resolution and sensitivity up to 100 pT/Hz$^{1/2}$.

physics.app-ph↗

arXiv2020

Surface lattice resonance based magneto-plasmonic switch in NiFe patterned nano-structure

In this work, a 2D magneto-plasmonic grating structure combining materials with ferromagnetic and plasmonic properties is demonstrated. NiFe composite ferromagnetic material, as an active medium with tunable physical properties, and Au metal, as a plasmonic excitation layer, were the materials of choice. Here, we have experimentally investigated the active control of the plasmonic characteristics in Au/NiFe bilayer by the action of an external magnetic field, as well as the switching effect of the system. The active plasmonic control, can be achieved by the magnetization switching of the ferromagnetic material, opening a new path in the development of active plasmonic devices. To our best knowledge, this is the first demonstration of such a magneto-optical plasmonic switch based on the coupling of plasmons with magneto-optical active materials, in which the response time was estimated to be in the range of microseconds.

physics.optics↗

arXiv2019

High-Q surface electromagnetic wave resonance excitation in magneto-photonic crystals for super-sensitive detection of weak light absorption in near-IR

Mid-infrared spectrum can be recorded from almost any material making the mid-infrared spectroscopy an extremely important and widely used sample characterization and analytical technique. However, sensitivity photoconductive detectors operate primarily in the near-infrared (NIR) but not in the mid-infrared making the NIR more favorable for accurate spectral analysis. Although absorption cross-section of vibrational modes in near-infrared is orders of magnitude smaller compared to the fundamental vibrations in mid-infrared, different concepts were proposed to increase the detectability of weak molecular transitions overtones. Yet, the contribution of magneto-photonic structures in near-infrared absorption effect has never been explored so far. Here we propose high-Q magneto-photonic structures for a super-sensitive detection of weak absorption resonances in near-infrared. We analyze the contributions of both magnetic and non-magnetic photonic crystal (PC) configurations to the detection of weak molecular transitions overtones. Our results constitute an important step towards development of highly sensitive spectroscopic tools based on high-Q magneto-photonic sensors.

physics.optics↗

arXiv2019

Peculiarities of the Faraday effect in gold-nanodisk/iron-garnet heterostructures

In this paper, matters considering the immersion of gold nanoparticles inside a magnetic medium are investigated experimentally and theoretically. Three samples with periodic arrays of Au cylinders where studied: particles on a surface of the magnetic dielectric film, inside the magnetic film and directly under the magnetic film. The largest LSPR mediated Faraday rotation resonance enhancement takes place for the case of the nanoparticles submerged inside the magnetic film. Optimal place for nanoparticles is under the magnetic medium surface at 6 nm deep in the considered configurations. It is shown that the most influence on the Faraday rotation enhancement is produced by the magnetic properties of the medium between the nanoantennas. The experimental results are in good agreement with the numerical analysis.

physics.optics↗

arXiv2018

Transverse Magneto-Optical Kerr Effect at Narrow Optical Resonances

Magneto-optical spectroscopy based on the transverse magneto-optical Kerr effect (TMOKE) is a sensitive method for investigation of magnetically-ordered media. However, in magnetic materials the optical transitions are usually characterized by spectrally broad resonances with widths considerably exceeding the Zeeman splitting in the magnetic field. Here we investigate experimentally and theoretically the TMOKE in the vicinity of relatively narrow optical resonances provided by confined quantum systems. For experimental demonstration we use the exciton resonance in a (Cd,Mn)Te diluted magnetic semiconductor quantum well, where the strong exchange interaction with magnetic ions enables the giant Zeeman splitting of exciton spin states $Δ$ in magnetic fields of a few Tesla. In the weak coupling regime, when the splitting $Δ$ is smaller than the spectral broadening of the optical transitions $Γ$, the TMOKE magnitude grows linearly with the increase of the Zeeman splitting and its spectrum has an S-shape, which remains virtually unchanged in this range. In the strong coupling regime ($Δ>Γ$) the TMOKE magnitude saturates, while its spectrum is strongly modified resulting in the appearance of two separate peaks. The TMOKE is sensitive not only to the sample surface but can be used to probe the confined electronic states in depth if the upper layer is sufficiently transparent. Our results demonstrate that TMOKE of spectrally narrow resonances serves as a versatile tool for probing the charge and spin structure of electronic states in various confined quantum systems and can be used for spin tomography in combination with the conventional polar Kerr effect.

cond-mat.mtrl-sci↗

arXiv2018

Optically Pumped Floquet States of Magnetization in Ferromagnets

Floquet states have been subject of great research interest since Zel'dovich's pioneering work on the quasienergy of a quantum system subject to a temporally periodic action. Nowadays periodic modulation of the system Hamiltonian is mostly achieved by microwaves leading to novel exciting phenomena in condensed matter physics: Floquet topological insulators, chiral edge states etc. On the other hand, nonthermal optical control of magnetization at picosecond time scales is currently a highly appealing research topic for potential applications in magnetic data storage. Here we combine these two concepts to investigate Floquet states in the system of exchange-coupled spins in a ferromagnet. We periodically perturb the magnetization of an iron-garnet film by a train of circularly-polarized femtosecond laser pulses hitting the sample at 1 GHz repetition rate and monitor the magnetization dynamics behaving like a Floquet state. An external magnetic field allows tuning of the Floquet states leading to a pronounced increase of the precession amplitude by one order of magnitude at the center of the Brillouin zone, i.e. when the precession frequency is a multiple of the laser pulse repetition rate. Floquet states might potentially allow for parametric generation of magnetic oscillations. The observed phenomena expand the capabilities of coherent ultrafast optical control of magnetization and pave a way for their application in quantum computation or data processing.

cond-mat.mes-hall↗

arXiv2018

TMOKE as efficient tool for the magneto-optic analysis of ultra-thin magnetic films

Ultra-thin magnetic dielectric films are of prime importance due to their applications for nanophotonics and spintronics. Here, we propose an efficient method for the magneto-optical investigation of ultra-thin magnetic films which allows one to access their state of magnetization and magneto-optical properties. It is based on the surface-plasmon-polariton-assisted transverse magneto-optical Kerr effect (TMOKE). In our experiments, sub-100 nm-thick bismuth-substituted lutetium iron-garnet films covered with a plasmonic gold grating have been analyzed. The excitation of surface plasmon-polaritons provides resonance enhancement of TMOKE up to 0.04 and makes it easily detectable in the experiment. For films thicker than 40 nm, the TMOKE marginally depends on the film thickness. A further decrease in the film thickness diminishes TMOKE since for such thicknesses the surface plasmon-polariton field partly penetrates inside the non-magnetic substrate. Nevertheless, the TMOKE remains measurable even for few-nm-thick films, which makes this technique unique for the magneto-optical study of ultra-thin films. Particularly, the proposed method reveals that the off-diagonal components of the magnetic film permittivity tensor grow slightly with the reduction of the film thickness.

physics.ins-det↗

arXiv2017

Excitation of magnon accumulation by laser clocking as a source of long-range spin waves in transparent magnetic films

Optical tools are of great promise for generation of spin waves due to the possibility to manipulate on ultrashort time scales and to provide local excitation. However, a single laser pulse can inject spin waves only with a broad frequency spectrum, resulting in a short propagation distance and low amplitude. Here we excite a magnetic garnet film by a train of fs-laser pulses with 1 GHz repetition rate so that pulse separation is smaller than decay time of the magnetic modes which allows to achieve collective photonic impact on magnetization. It establishes a quasi-stationary source of SWs, namely a coherent magnon accumulation ("magnon cloud"). This approach has several appealing features: (i) the source is tunable; (ii) the SW amplitude can be significantly enhanced; (iii) the spectrum of the generated SWs is quite narrow that provides longer propagation distance; (iv) the periodic pumping results in almost constant in time SW amplitude up to 100 um away from the source; and (v) the SW emission shows a pronounced directionality. These results expand the capabilities of ultrafast coherent optical control of magnetization and pave a way for applications in data processing, including the quantum regime. The quasi-stationary magnon accumulation might be also of interest for the problem of magnon Bose-Einstein condensate.

cond-mat.mes-hall↗

arXiv2016

On the correlation of light polarization in uncorrelated disordered magnetic media

Light scattering in a magnetic medium with uncorrelated inclusions is theoretically studied in the approximation of ladder diagram. Correlation between polarizations of electromagnetic waves that are produced by infinitely-distant dipole source is considered. Here white noise disorder model with Gaussian distribution is taken into account. In such a medium the magneto-optical interaction leads to correlation between perpendicular light polarizations. Spatial field correlation matrix with nonzero nondiagonal elements is obtained in the first order on gyration.

physics.optics↗

arXiv2016

Enhancement of electron hot spot relaxation in photoexcited plasmonic structures by thermal diffusion

We demonstrate that in confined plasmonic metal structures subject to ultra-fast laser excitation electron thermal diffusion can provide relaxation faster than the energy transfer to the lattice. This relaxation occurs due to excitation of nanometer-sized hot spots in the confined structure and the sensitivity of its optical parameters to the perturbation in these regions. Both factors become essential when the plasmonic resonance condition is met for both excitation and detection. A pump-probe experiment on plasmonic gold lattices shows sub-picosecond relaxation with the characteristic times well-described by a two-temperature model. The results suggest that dynamical optical response in plasmonic structures can be tuned by selection of the structural geometry as well as the choice of wavelength and polarization of the excitation and detection light.

cond-mat.mtrl-sci↗

arXiv2012

Near dispersion-less surface plasmon polariton resonances at a metal-dielectric interface

Omni-directional light coupling to surface plasmon polariton (SPP) modes to make use of plasmon mediated near-field enhancement is challenging. We report possibility of near dispersion-less modes in structures with unpatterned metal-dielectric interfaces having 2-D dielectric patterns on top. We show that the position and dispersion of the excited modes can be controlled by the excitation geometry and the 2-D pattern. The anti-crossings resulting from the in-plane coupling of different SPP modes are also shown.

cond-mat.mtrl-sci↗

arXiv2011

Plasmonic crystals for ultrafast nanophotonics: Optical switching of surface plasmon polaritons

We demonstrate that the dispersion of surface plasmon polaritons in a periodically perforated gold film can be efficiently manipulated by femtosecond laser pulses with the wavelengths far from the intrinsic resonances of gold. Using a time- and frequency- resolved pump-probe technique we observe shifting of the plasmon polariton resonances with response times from 200 to 800 fs depending on the probe photon energy, through which we obtain comprehensive insight into the electron dynamics in gold. We show that Wood anomalies in the optical spectra provide pronounced resonances in differential transmission and reflection with magnitudes up to 3% for moderate pump fluences of 0.5 mJ/cm^2.

cond-mat.mtrl-sci↗

arXiv2011

Inverse Transverse Magneto-Optical Kerr Effect

It is demonstrated that a static in-plane magnetic field is generated in a ferromagnetic film by p-polarised light obliquely incident on the film. This phenomenon can be called inverse transverse magneto-optical Kerr effect. The femtosecond laser pulse of peak intensity of 500 W/μm2 generates in nickel an effective magnetic field of about 100 Oe. The value of the effective magnetic field can be increased by more than an order of magnitude at the surface plasmon polariton resonance excited in smooth metal dielectric structures or in plasmonic crystals.

cond-mat.other↗

arXiv2010

Extraordinary Magnetooptics in Plasmonic Crystals

Plasmonics has been attracting considerable interest as it allows localization of light at nanoscale dimensions. A breakthrough in integrated nanophotonics can be obtained by fabricating plasmonic functional materials. Such systems may show a rich variety of novel phenomena and also have huge application potential. In particular magnetooptical materials are appealing as they may provide ultrafast control of laser light and surface plasmons via an external magnetic field. Here we demonstrate a new magnetooptical material: a one-dimensional plasmonic crystal formed by a periodically perforated noble metal film on top of a ferromagnetic dielectric film. It provides giant Faraday and Kerr effects as proved by the observation of enhancement of the transverse Kerr effect near Ebbesen's extraordinary transmission peaks by three orders of magnitude. Surface plasmon polaritons play a decisive role in this enhancement, as the Kerr effect depends sensitively on their properties. The plasmonic crystal can be operated in transmission, so that it may be implemented in devices for telecommunication, plasmonic circuitry, magnetic field sensing and all-optical magnetic data storage.

cond-mat.other↗