Vladimir Drachev

• PhD
• Professor (Associate) at University of North Texas

The paper describes results of the numerical simulation and experimental characterization of plasmonic gratings and waveguides in the optical range of 1520 – 1630 nm. Gold structures were coated with a 630-nm thick tetraethylorthosilicate layer to achieve higher coupling efficiency for plasmonic gratings using lensed optical probes. We experimental...

Cortisol is a steroid hormone that regulates energy metabolism, stress reactions, and immune response. Cortisol is produced in the kidneys’ adrenal cortex. Its levels in the circulatory system are regulated by the neuroendocrine system with a negative feedback loop of the hypothalamic–pituitary–adrenal axis (HPA-axis) following circadian rhythm. Co...

Minority hole diffusion length and lifetime were measured in independent experiments by electron beam-induced current and time-resolved cathodoluminescence in Si-doped β-Ga2O3 Schottky rectifiers irradiated with 18 MeV alpha particles and 10 MeV protons. Both diffusion length and lifetime exhibited a decrease with increasing temperature. The non-eq...

A metal-dielectric interface is usually modeled by a zero-width layer, where dielectric permittivity suffers a discontinuity jump. In reality, there is a narrow transition region, which includes an epsilon-near-zero (ENZ) layer. We show that due to a continuous dielectric function the dispersion of the surface plasmon is modified. The energy of the...

Here we discuss effect of spin-polarization on plasmon excitation in deep ultra-violet spectral range for Co nanoparticles with a single-domain magnetic structure. Structural, magnetic, and optical characterizations of Co nanoparticles shine a light on a mechanism of the magneto-plasmonic response.

Indium tin oxide is often used as an active material in photonics. Strong correlation between its optical response and a state of conduction electrons, as well as an intermediate density of charges typical for semiconductors, makes it highly tunable using an external electric field. This property is extensively used in various types of electro-opti...

In our work we investigate the propagation of optical modes in nanoscale hybrid plasmonic waveguides. Frequency domain Maxwell equations based simulations are implemented to study properties of mixed modes in 3D. The results of our analysis are applied to design an advanced hybrid waveguide with useful characteristics. It is demonstrated here how t...

Cortisol is a steroid hormone that regulates a wide range of vital processes. Its level changes with diurnal rhythm and reacts on stress. Measurement of cortisol levels is still a complex multi-step process. A reversible washing-free registration method is required. Here we describe metal-enhanced fluorescence assay based on displacement of a dye l...

Endogenous autofluorescence of biological tissues is an important source of information for biomedical diagnostics. Despite the molecular complexity of biological tissues, the list of commonly known fluorophores is strictly limited. Still, the question of molecular sources of the red and near-infrared excited autofluorescence remains open. In this...

We have used a full quantum mechanical approach to study the second-order correlation function of a system of a few two-level atoms coupled via plasmons. By the usage of quantum regression theory we have developed a new model that allows us to fully investigate the dependence of photon bunching and anti-bunching effects to the interaction between a...

An efficient electro-optical modulation has been demonstrated here by using an edge plasmon mode specific for the hybrid plasmonic waveguide. Our approach addresses a major obstacle of the integrated microwave photonics caused by the polarization constraints of both active and passive components. In addition to sub-wavelength confinement, typical f...

An efficient electro-optical modulation has been demonstrated here by using an edge-plasmon mode specific for the hybrid plasmonic waveguide. Our approach addresses a major obstacle of the integrated microwave photonics caused by the polarization constraints of both active and passive components. In addition to subwavelength confinement, typical fo...

A combination of computational power provided by modern MOSFET-based devices with light assisted wideband communication at the nanoscale can bring electronic technologies to the next level. Obvious obstacles include a size mismatch between electronic and photonic components as well as a weak light–matter interaction typical for existing devices. Po...

A new type of bimodal contrast agent was made that is based on the self-quenching of indocyanine green (ICG) encapsulated in a biocompatible and biodegradable polymer shell. The increasing of a local ICG concentration that is necessary for the obtaining of self-quenching effect was achieved by freezing-induced loading and layer-by-layer assembly. A...

Blood cell analysis is one of the standard clinical tests. Despite the widespread use of exogenous markers for blood cell quantification, label-free optical methods are still of high demand due to their possibility for in vivo application and signal specific to the biochemical state of the cell provided by native fluorophores. Here we report the re...

Here it is experimentally shown that Co nanoparticles with a single-domain crystal structure support a plasmon resonance at approximately 280 nm with better quality than gold nanoparticle resonance in the visible. Magnetic nature of the nanoparticles suggests a new type of these plasmons. The exchange interaction of electrons splits the energy band...

Protein assisted-, DNA hybridized- plasmonic nanostructures for the visible, fractal shell core-less for the extremely broad band VIS-IR and magnetic nanoparticles for the deep UV involved in our efforts on biosensing including cortisol probe.

Hybrid plasmonic waveguides with an embedded conducting oxide layer can be used for producing fast and compact electro-optical modulation devices. However, due to constraints, which plasmon modes impose on light polarisation, modulators of this class are not compatible with high-efficiency modern diffraction gratings used for coupling light into a...

Coupled super- and sub- radiant emission of dye fluorescence near the plasmonic surface is shown to be an intrinsic property of the hybrid system. The bi-exponential decay is demonstrated for Au\SiO2\ATTO655 core-shell nanoparticles, which persists even when averaging over a broad range of the coupling parameter. The superradiant and subradiant sta...

Bi-exponential decay of dye fluorescence near the surface of plasmonic metamaterials and core-shell nanoparticles is shown to be an intrinsic property of the coupled system. Indeed, the Dicke, cooperative states involve two groups of transitions: super-radiant, from the most excited to the ground states and sub-radiant, which cannot reach the groun...

Gratings with complex multilayer strips are studied under inclined incident light. Great interest in these gratings is due to applications as input/output tools for waveguides and as subwavelength metafilms. The structured strips introduce anisotropy in the effective parameters, providing additional flexibility in polarization and angular dependenc...

Gold dipole nanoantennas embedded in an organic molecular film provide strong local electromagnetic fields to enhance both the nonlinear refractive index (n2) and two-photon absorption (2PA) of the molecules. An enhancement of 53× for 2PA and 140× for nonlinear refraction is observed for BDPAS (4,4'-bis(diphenylamino)stilbene) at 600 nm with only 3...

The research field of metamaterials is reaching its maturity, encouraging one to actively search for real-life applications of the metamaterial concept. This issue features works covering various aspects of metadevices—a natural progression of the paradigm that aims to accommodate and dynamically control metamaterial response in miniature photonic...

Plasmonic resonances of the metallic shells depend on their nanostructure and geometry of the core, which can be optimized for the broadband extinction normalized by mass. The fractal nanostructures can provide a broadband extinction. It allows as well for a laser photoburning of holes in the extinction spectra and consequently windows of transpare...

We propose an analytical approach for calculation of the homogenized dielectric functions ε∥(ω) and ε⊥(ω) of one-dimensional periodic metal-dielectric structure. The obtained formulas are valid at high frequencies near the points of topological transition from an elliptic to hyperbolic regime. The proposed method of high-frequency homogenization ta...

A method for retrieving effective n2 and α from bianistropic parameters of non-linear metasurfaces is introduced. The effective nonlinear parameters of a metasurface covered by a NL layer are compared vs a bare NL layer.

Significant extinction from the visible to mid-infrared makes fractal shells very attractive as aerosolized obscurants. In contrast to the planar fractal films, where the absorption and reflection equally contribute to the extinction, the shells’ extinction is caused mainly by the absorption. The Mie scattering resonance at 560 nm of a silica core...

The scattering and absorption suppression of the silica microspheres is experimentally achieved by semicontinuous gold shell synthesized on the silica microspheres. These fractal gold shells on the silica spheres are shown to have significant extinction in the visible and mid-infrared spectral range. It is found that the silica scattering peak in t...

A tunable super-lens (TSL) for nanoscale optical sensing and imaging of bio-molecules and nano-manufacturing utilizes negative-index materials (NIMs) that operate in the visible or near infrared light. The NIMs can create a lens that will perform sub-wavelength imaging, enhanced resolution imaging, or flat lens imaging. This new TSL covers two diff...

Scandium nitride (ScN) is a rocksalt semiconductor that has attracted significant attention from various researchers for a diverse range of applications. Motivated by the prospect of using its interesting electronic structure for optoelectronic and dilute magnetic semiconductor applications, we present detailed studies of the electronic transport a...

In diffractive optics, typical feature sizes are on the order of the wavelength—around 1 μm for visible and near-infrared light. Although nanometer-scale features do not diffract optical waves, nanosized structures could enable us to design novel diffractive optical devices. Plasmonics and metamaterials are the two ways to couple light into nanosca...

Hyperbolic materials enable numerous surprising applications that include far-field subwavelength imaging, nanolithography, and emission engineering. The wavevector of a plane wave in these media follows the surface of a hyperboloid in contrast to an ellipsoid for conventional anisotropic dielectric. The consequences of hyperbolic dispersion were f...

We demonstrate high resonant absorption of visible light with a plasmonic nanocavity chain structure fabricated through resistless nanoimprinting in metal (RNIM). The RNIM approach provides a simple, reproducible, and accurate means to fabricate metallic nanopatterns with high fidelity. The nanocavities are shown to be efficiently excited using nor...

We present new types of focusing devices consisting of metallic nanoslits with proof-of-concept experiments. Polarization-selective nanoslit lenses can focus or defocus linearly polarized light depending on the incident polarization. The interference peak from double slits inside a strongly anisotropic medium becomes sub-wavelength. We also present...

Experiments demonstrate that inside strongly anisotropic materials with hyperbolic dispersion, light diffracted from double slits propagates as volume plasmon polaritons and form subwavelength interference peaks that can be used in subwavelength photolithography and probes.

Inside of a hyperbolic medium, the principal components of the permittivity tensor have opposite signs causing the medium to exhibit a ‘metallicbr’ type of response to light wave sin one direction, and a ‘dielectric’ response in the other. Our study shows that inside hyperbolic media, volume plasmon polaritons (VPPs) propagate along the characteris...

Sonication with nucleic acids has become a standard method for obtaining aqueous dispersions of carbon nanotubes. On the basis of theoretical studies and scanning probe microscopy (SPM) imaging a widely accepted model for DNA association with SWCNT is one in which the DNA binds through non-covalent π-stacking and hydrophobic interactions. Following...

In this paper, we explore the use of magnetic resonant metamaterials, so called metamagnetics, as dispersive elements for optical pulse shaping. We measure both positive and negative group delay dispersion (GDD) values in a metamagnetic material using the multiphoton interference phase scan (MIIPS) technique and show pulse temporal profiles numeric...

Creating a subwavelength focus spot from nanoslits becomes possible when diffraction occurs inside strongly anisotropic materials with hyperbolic dispersion. In this work, we study diffraction from nanoslits and numerically show that the interference patterns could be smaller than λ/10. The designs studied in this work are feasible with current nan...

We directly demonstrate an improvement in the radiative decay rate of dye molecules near multilayer hyperbolic metamaterials (HMMs). Our comprehensive study shows a radiative decay rate for rhodamine 800 (Rh800) that is several times higher due to the use of HMM samples as compared to dielectric substrates. This is also the first experimental demon...

Broad-band, mass-normalized extinction cross-sections up to 1m2/g are demonstrated using chemically modified gold fractal nanostructures grown on silica microparticles.

We numerically investigate a sub-class of metamaterials with anisotropic structural elements. We show such a metamaterial allows for placing electric and magnetic resonance bands close together, hence providing flexible manipulation of optical pulses.

Our experiment demonstrates a subwavelength-wide peak from double-slit diffraction inside a slab with hyperbolic dispersion; this highly localized field can be used for subwavelength probes.

Nanostructured plasmonic metamaterials, including optical nanoantenna arrays, are important for advanced optical sensing and imaging applications including surface-enhanced fluorescence, chemiluminescence, and Raman scattering. Although designs typically use ideally smooth geometries, realistic nanoantennas have nonzero roughness, which typically r...

The focusing properties of gold nanoslit lenses are controlled by changing the refractive index of liquid crystal fillings inside the nanoslits. When the liquid crystals are in the isotropic state, the nanoslit lenses have higher transmission than in the case when the liquid crystals are in the nematic state. Additionally, the lens that focuses TM-...

Approaches to the adequate homogenization of optical metamaterials are becoming more and more complex, primarily due to an increased understanding of the role of asymmetric electrical and magnetic responses, in addition to the nonlocal effects of the surrounding medium, even in the simplest case of plane-wave illumination. The current trend in deve...

This focus issue of Optical Materials Express reflects new trends in nanoplasmonics and metamaterials presented by leading groups in the field.

Effects of a solid matrix on the dye kinetic parameters for Rh800 were experimentally studied. Saturation intensity dependencies were measured with a seeding pulse amplification method using a picosecond and a femtosecond white light supercontinuum source. The kinetic parameters were obtained by fitting experimental dependencies with Yee’s finite-d...

Historically, the methods used to describe the electromagnetic response of random, three-dimensional (3D), metal-dielectric composites (MDCs) have been limited to approximations such as effective-medium theories that employ easily-obtained, macroscopic parameters. Full-wave numerical simulations such as finite-difference time domain (FDTD) calculat...

We experimentally demonstrate the focusing properties of arrays of parallel subwavelength-wide nanoslits in a gold film. The lenses are designed to focus either TM- or TEpolarized light and diverge the light of the orthogonal polarization.

We present an ADE-FDTD model of gain media fitted to pump-probe experiments with Rh800-epoxy composite deposited on glass substrate. The experiment-fitted parameters of the 4-level ADE system are instrumental to modeling active nanoplasmonic devices.

A part of the sentence just before Eq. (1) in our previous Letter [Opt. Lett. 36, 451 (2011)] was incorrect and is corrected here.

We present comprehensive studies on thin diffraction lenses made of arrays of subwavelength, parallel nanoslits in a gold film. Such a nanoslit lens can operate either as a conventional convex or concave lens. The lenses can be designed to focus linearly polarized light with polarization either perpendicular (TM-lens) or parallel to the slits (TE-l...

Effective identification of breast cancer stem cells (CSC) benefits from a multiplexed approach to detect cell surface markers that can distinguish this subpopulation, which can invade and proliferate at sites of metastasis. We present a new approach for dual-mode sensing based on targeting using pointer and signal enhancement using enhancer partic...

We present an ADE-FDTD model of gain media fitted to pump-probe experiments with dye(Rh800)-epoxy composite deposited on ITO-silica substrate. The experiment-fitted parameters of the 4-level ADE system are instrumental to modeling active nanoplasmonic devices.

We use a nanofabricated gold grating to validate two-dimensional spatial harmonic analysis (2D SHA) method, also known as Fourier modal method or rigorous coupled-wave analysis under oblique incidence. The transmittance spectra of the metal grating for incident angles of 0°–30° are obtained in both experiments and simulations at the zero diffractio...

Tunable and active metamaterials can enable a new powerful paradigm of engineering space for light with transformation optics, leading to a family of new applications ranging from a planar hyperlens to optical black hole.

The recently emerged fields of metamaterials and transformation optics promise a family of exciting applications such as invisibility, optical imaging with deeply subwavelength resolution and nanophotonics with the potential for much faster information processing. The possibility of creating optical negative-index metamaterials (NIMs) using nanostr...

We have employed a parallelized 3D FDTD (finite-difference time-domain) solver to study the electromagnetic properties of random, semicontinuous, metal films. The structural features of the simulated geometries are exact copies of the fabricated films and are obtained from SEM images of the films themselves. The simulation results show good agreeme...

Gold dipole nanoantennas which have strong local electromagnetic fields are used to enhance two-photon absorption. A 30 to 40 times enhancement is observed for BDPAS (4,4'-bis(diphenylamino)stilbene) at 600 nm.

Sub-wavelength gratings of paired Ag strips are measured and analyzed using spectroscopic ellipsometry, and show significant angular dependence of the electric and magnetic resonance properties, along with evidence of bi-anisotropy.

We use spatial harmonic analysis (SHA) to model gold double-strip gratings under obliquely incident light. The simulation results are compared to experimentally measured values and excellent matches are achieved.

Owing to the low-loss and high refractive index variations derived from the basic building block of bone structure, we, for the first time to our knowledge, demonstrate coherent random lasing action originated from the bone structure infiltrated with laser dye, revealing that bone tissue is an ideal biological material for random lasing. Our numeri...

We, for the first time, demonstrate coherent random lasing action in bone tissue infused with laser dye. This could potentially be used to probe structural alterations at nanoscales in real-time as a novel spectroscopic modality.

The effect of grain boundaries on the electron relaxation rate is significant even for large area noble metal films and more so for plasmonic nanostructures. Optical spectroscopy and X-ray diffraction show a substantial improvement in plasmon resonance quality for square-particle nanoantennas after annealing due to an enlarged grain size from 22 to...

We present a comprehensive study of the structural and electronic properties of ultrathin films containing graphene layers synthesized by chemical vapor deposition based surface segregation on polycrystalline Ni foils then transferred onto insulating SiO ₂/ Si substrates. Films of size up to several mm’s have been synthesized. Structural...

We have studied the effect of aperture-sample interactions on the near-field optical imaging and its application for plasmonic metamaterials. Specifically, periodic arrays of paired and single gold nanorods were studied at the near-field using reflection and transmission modes of a near-field scanning optical microscope (NSOM) at various wavelength...

Metal nanoantenna arrays are typically designed and simulated using an ideal (smooth) geometry, and degraded experimental performance due to surface roughness, interior defects, and other effects are taken into account through a single value, a material `loss factor'; although a 2-D roughness has been introduced in simulations for plasmonic metamag...

Improvements in energy damage threshold of gold nanoantennas were studied using stabilizing dielectric films. Annealed nanoantennas show a stronger plasmonic resonance, but have a decreased damage threshold.

A well-established, silver fishnet design has been further miniaturized to function as a negative-index material at the shortest wavelength to date (to our knowledge). By studying the transmittance, reflectance, and corresponding numerical simulations of the sample, we report in this Letter a negative refractive index of − 0.25 at the yellow-light...

We demonstrate a thermally tunable optical metamaterial with negative permeability working in the visible range. By covering coupled metallic nanostrips with aligned nematic liquid crystals (NLCs), the magnetic response wavelength of the metamaterial is effectively tuned through control of the ambient temperature, changing the refractive index of L...

The optical forces between coupled metal nanoparticles are strongly enhanced by high field gradients that is currently of great interest for nanoscale optical manipulation such as "optical nanotweezers". A special case arises when the light induced forces are comparable with the relatively weak forces, such as the dispersion ones, as well as the el...

We report on a metamaterial sample that demonstrates double-negative index behavior at the shortest wavelength to date. We also discuss the controlled resonance tuning of optical magnetism in materials by using of liquid crystals.

Our simulations show that highly localized field enhancement produced by a periodic array of silver nanoantennas can be translated to the far side of a metal-dielectric composite superlens composed of silver and silica components.

The optical coefficients of a nonlinearity for a macroscopic ensemble of aggregates of metal nanoparticles that is caused by deformation of the spatial structure of clusters in a strong light field are calculated for the first time. For a continuous medium that consists of a nonabsorbing dielectric containing aggregated silver nanoparticles that do...

We report on a metamaterial sample that demonstrates double-negative index behavior at the shortest wavelength to date. We also discuss the controlled resonance tuning of optical magnetism in materials by using of liquid crystals.

Our simulations show that highly localized field enhancement produced by a periodic array of silver nanoantennas can be translated to the far side of a metal-dielectric composite superlens composed of silver and silica components.

We review recent progress in optical metamaterials and demonstrate our sample with negative index behavior at the shortest wavelength so far (710 nm). We discuss the impact of fabrication limitations on the performance of metamaterials.

A motion-induced optical bistability is shown for a metal nanoparticle dimer that is plasmon coupled and bound with dispersion (colloidal) forces. The effect does not require any material nonlinearity.

Enhanced fluorescence is observed from dye molecules interacting with optical nanoantenna arrays. Elliptical gold dimers form individual nanoantennae with tunable plasmon resonances depending upon the geometry of the two particles and the size of the gap between them. A fluorescent dye, Rhodamine 800, is uniformly embedded in a dielectric host that...

Optical nanoantennae are developed for their field enhancement properties. Dye coating antenna arrays show enhanced fluorescence that varies with antenna geometry. The enhanced fluorescence exhibits a reduced excited state lifetime and a dipolar polarization pattern.

We have synthesized and studied hybrid Au/silica/dye nanoparticles. We have demonstrated that the reduction of the thickness of silica shell separating gold and dye causes the reduction of nanoparticles’ absorption and strong enhancement of emission intensity.

Nanoantenna plasmonic absorption is enhanced using an annealing technique. The annealed Au nanoantenna array shows sharper resonances and twice the peak absorption versus those in the initially fabricated array before annealing.

Periodic arrays of paired and single gold nanorods were imaged in the near field using reflection and transmission modes of a near-field scanning optical microscope at various wavelengths and polarizations of light in the visible range. The paired nanorods act like nanoantenna, and an array of them was initially designed as a negative-index materia...

The optical properties of semicontinuous silver films have been studied in the mid infrared. The film extinction spectra are shown to be well tailored by the deposition conditions and post-fabrication photomodification with both nanosecond and picosecond laser pulses at 10.6 mu m. The photomodification results in a decrease of the extinction above...

A new class of artificially structured materials called metamaterials makes it possible to achieve electromagnetic properties that do not exist in nature. In this article, we review the recent progress made in the area of optical metamaterials, specifically artificial magnetism and negative-index metamaterials. It was predicted that nanostructured...

A material parameter extraction procedure for general BI metamaterials has been presented. The retrieved material parameters correspond to those of the homogeneous BI material slab of the same thickness that produces the same transmission and reflection properties. A doubly-periodic chiral NIM design in the near-IR spectrum has been presented along...

A new class of artificially structured materials called metamaterials makes it possible to achieve electromagnetic properties that do not exist in nature. In this paper we review the recent progress made in the area of optical metamaterials. It was predicted that nanostructured metamaterials could provide us with artificial magnetic response and ne...

Plasmonic filters were fabricated based on gold fractal nanostructures grown on silica microspheres. The fractal nanostructures were modified using laser irradiation, resulting in decreased extinction in the mid-infrared range.