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Papers by Sergey Gaponenko

ACS Nano, 2013

Pronounced 10 4-fold enhancement of Raman scattering has been obtained for ZnO nanocrystals on su... more Pronounced 10 4-fold enhancement of Raman scattering has been obtained for ZnO nanocrystals on substrates coated with 50 nm Ag nanoparticles under non-resonant excitation with a commercial red-emitting laser. This makes feasible beyond 10-18 mole detection of ZnO nanocrystals with a commercial setup using 0.1 mW continuous wave laser and can be

Applied Physics B Laser and Optics, 1994

Steady-state, time-resolved and polarizationresolved fluorescence studies of glasses doped with a... more Steady-state, time-resolved and polarizationresolved fluorescence studies of glasses doped with acridine orange with concentrations near 10-3 M/L are reported. It was found that at this concentration a noticeable part of dye molecules exists in the form of dimers. By means of a polarization-resolved spectroscopic technique the structure of dimers was found to be consistent with the simple exciton theory.

We propose to consider multilayer spatial structures as numbers. An arbitrary finite sequence of ... more We propose to consider multilayer spatial structures as numbers. An arbitrary finite sequence of layers with N values of a material parameter which determines the speed of wave propagation is considered as a number written in the numeration system with base N. Within the framework of this approach propagation of classical waves and quantum particles can be treated as number recognition. A problem is formulated of identification of a type among spatial sequences featuring unique spectral portraits versus spatial structure. It is shown possible to perform certain arithmetic operations by means of sequential propagation of waves through several structures. Using fractal Cantor structures as a representative example, spectral properties of waves are shown to reproduce certain properties of the corresponding numbers. A possibility is outlined to use the above approach for data storage. If a set of numbers possessing unique spectral portraits forms a complete set, then compact coding of a...

$Research paper thumbnail of Rationale for <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>1</mn><msup><mn>0</mn><mn>14</mn></msup></mrow><annotation encoding="application/x-tex">10^{14}</annotation></semantics></math>1014 enhancement factor in single molecule Raman spectroscopy$

arXiv: Optics, 2008

We extend the Purcell's original idea [Phys. Rev. \textbf{69}, 682 (1946)] on modification of... more We extend the Purcell's original idea [Phys. Rev. \textbf{69}, 682 (1946)] on modification of photon spontaneous \textit{emission} rate to modification of photon spontaneous \textit{scattering} rate. We find the interplay of local incident field enhancement and local density of photon states enhancement in close proximity to a silver nanoparticle may result in up to 101410^{14}1014-fold rise of Raman scattering cross-section. Thus single molecule Raman detection is found to be explained by consistent quantum electrodynamic description without any chemical mechanism involved. A model of the so-called "hot points" in surface enhanced spectroscopy has been elaborated as local areas with high Q-factor at incident and scattered (emitted) light frequencies. For verification of the model we consider further experiments including transient Raman experiments to clarify incident field enhancement and scanning near-field optical mapping of local density of photon states.

Plasma supports electromagnetic waves propagation for frequencies higher than plasma frequency bu... more Plasma supports electromagnetic waves propagation for frequencies higher than plasma frequency but features dielectric permittivity less than 1. This property leads to photon density of states (DOS) lower than in vacuum and should result in subnatural spectral linewidths, sub-Planckian spectrum of thermal radiation, and in sub-Rayleigh photon scattering as well as in lower inelastic photon scattering including Raman scattering in molecular and crystalline structures. We emphasize the basic character of these phenomena though absolute values of corrections from this property of plasmas in many real experiments may appear to be small as compared to other factors. We found that dissipative losses when being taken into account make possible DOS effects smaller though not vanishing and additionally bring about indefinite growth of DOS in the low-frequency limit. Introduction. -Photon density of states (DOS) in homogeneous space D(k) = k/π with k being the wave number of the mode in which...

AIP Advances

High-efficiency and low-loss gallium nitride dielectric metasurfaces for nanophotonics at visible... more High-efficiency and low-loss gallium nitride dielectric metasurfaces for nanophotonics at visible wavelengths

Abstract. A simple chemical technique was devised for the fabrication of silver nanostructured su... more Abstract. A simple chemical technique was devised for the fabrication of silver nanostructured substrates which can be used for plasmonic enhancement of labeled proteins fluorescence. For bovine serum albumin labeled with fluorescein isothiocyanate, the obtained enhancement factor ranges from three to seven, depending on metal-luminophore spacing and silver nanoparticle size. For excitation with linear polarized light, the enhancement factor increases noticeably for p-polarization and decreases for s-polarization. The experimental results were interpreted in terms of the theoretical model in which the enhancement factor depends on incident light polarization, luminophoremetal spacing and silver nanoparticle size. Proposed plasmonic substrates can be considered as an affordable replacement of standard ones in different types of fluorescent assays for the purpose of increasing sensitivity.

Journal of Experimental and Theoretical Physics Letters, 2001

The Journal of Physical Chemistry C, 2012

ABSTRACT Metal-enhanced fluorescence of molecular probes in plasmonic nanostructures offers highl... more ABSTRACT Metal-enhanced fluorescence of molecular probes in plasmonic nanostructures offers highly sensitive chemical and biomedical analyses, but a comprehensive theory of the phenomenon is far from being complete. In this study, a systematic theoretical analysis is provided for overall luminescence enhancement/quenching for fluorophores near silver spherical nanoparticles. The approach accounts for local intensity enhancement, radiative and nonradiative rates modification, light polarization, molecule position, and its dipole moment orientation. Numerical modeling has been performed for fluorescein-based labels (e.g., Alexa Fluor 488) widely used in biomedical studies and development. The maximal enhancement exceeding 50 times is predicted for nanoparticle diameter 50 nm, the optimal excitation wavelength being 370 nm. For long-wave excitation, bigger particles are more efficient. The experiments with a fluorescein isothiocyanate conjugate of bovine serum albumin confirmed theoretical predictions. The results provide an extensive and promising estimate for simple and affordable silver-based nanostructures to be used in fluorescent plasmonic sensors.

$Research paper thumbnail of Using high refractive index nanoparticles to inhibition of spontaneous emission$

Doklady of the National Academy of Sciences of Belarus

The article discusses the issues of inhibition of spontaneous emission of molecules by using sil... more The article discusses the issues of inhibition of spontaneous emission of molecules by using silicon spherical nanoparticles and dimers made from them. It is shown that at different wavelengths of the visible spectral range, the value of the total spontaneous transitions rate in a molecule located at an optimal distance with respect to the structure with silicon nanospheres and at an optimal size of the structure can be up to 5–10 times lower than the transition rate in the case when the nanoparticles are absent.

Optical Materials Express

physica status solidi (b)

Plasmonics

Emerging LED-based wireless visible light communication (Li-Fi) needs faster LED response to secu... more Emerging LED-based wireless visible light communication (Li-Fi) needs faster LED response to secure desirable modulation rates. Decay rate of an emitter can be enhanced by plasmonics, typically by an expense of efficiency loss because of non-radiative energy transfer. In this paper, metal-enhanced radiative and non-radiative decay rates are shown to be reasonably balanced to get with Ag nanoparticles nearly 100-fold enhancement of the decay rate for a blue LED without loss in overall efficacy. Additionally, gain in intensity occurs for intrinsic quantum yield Q 0 < 1. With silver, rate enhancement can be performed through the whole visible. For color-converting phosphors, local field enhancement along with decay rate effects enable 30-fold rate enhancement with gain in efficacy. Since plasmonics always enhances decay rate, it can diminish Auger processes thus extending LED operation currents without efficiency droop. For quantum dot phosphors, plasmonic diminishing of Auger processes will improve photostability.

$Research paper thumbnail of Colloidal Photoluminescent Refractive Index Nanosensor Using Plasmonic Effects$

Zeitschrift für Physikalische Chemie

Fluorescence enhancement by metal nanostructures which is sensitive to refractive index n of an a... more Fluorescence enhancement by metal nanostructures which is sensitive to refractive index n of an ambient medium is suggested as an operation principle of a novel refractive index sensor for liquids. Calculations are made for spherical and spheroidal Ag particles, and potential feasibility of sensitivity of the order of Δn=10−4 is demonstrated. Sensors of this type can be made fully colloidal with metal bodies deposited on a substrate or comprising a metal layer covering colloidal assembly of dielectric particles to serve as a test strip as well as placed on a fiber tip end to get local probing of refractive index in the tip-enhanced refractometry mode. Colloidal core-shell semiconductor nanocrystals may become the best candidates for this type of sensors whereas molecular probes may be affected by chemical properties of tested liquids.

$Research paper thumbnail of Optical filters based on fractal and aperiodic multilayers$

Procedia Engineering, 2016

ABSTRACT We report on experimental and theoretical investigation of birefringence of free-standin... more ABSTRACT We report on experimental and theoretical investigation of birefringence of free-standing nanoporous anodic alumina membranes in the optical range. The value of birefringence is analyzed for the samples with different porosities by measuring polarization dependent transmission spectra at different angles of incidence. The experimental data are compared to the results of birefringence simulations in accordance with three simulation approaches: modified Bruggeman effective-medium approximation, Boundary conditions model, plane-wave expansion method. It is both experimentally and theoretically shown that birefringence value increases with porosity increasing in the low porosity region. The porous alumina samples under investigation possess greatest value of birefringence (0.062) up to date.

We have carried out an experimental study of the nonlinear optical properties of multilayer heter... more We have carried out an experimental study of the nonlinear optical properties of multilayer heterostructures based on zinc chalcogenides when excited by ultrashort laser pulses. We have observed a strong change in the optical properties of the samples over a broad spectral region for two-photon and one-photon excitation of the ZnSe sublattice. The fast relaxation time of the nonlinearity is ~2-5 psec in both cases. We propose a physical model qualitatively explaining the observed effects.