Mykhailo Brodyn

Mykhailo Brodyn
National Academy of Sciences of Ukraine | ISP · Institute of Physics

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119
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Publications

Publications (119)
Article
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Твердi щiльно-упакованi плiвки напiвпровiдникових нанокристалiв (НК) проявляють специфiчнi оптоелектроннi властивостi, зумовленi сильною квантовою взаємодiєю I гiбридизацiєю орбiталей екситонiв мiж НК. Це вiдкриває шляхи до створення нових штучних свiтлозбираючих комплексiв та фотовольтаїчних структур з просторовим роздiленням електронiв та дiрок....
Article
Nonlinear optical properties of thin polycrystalline PdO films are investigated using the Z-scan technique and a 800 nm 180 fs laser, whose wavelength is significantly longer than the absorption edge at 500 nm. Cubic nonlinear susceptibility Re χ⁽³⁾ = +1.1 × 10⁻⁶ esu (n2 = 5.6 × 10⁻⁹ cm²/W) and nonlinear absorption coefficient β ≈ 5 × 10⁻⁵ cm/W are...
Article
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Semiconductor quantum dots are promising nanostructures for their application in solar cells of the 3rd generation, photodetectors, light emitting diodes, and as biological markers. However, the issue concerning the influence of superficial organic stabilizers (ligands) on the energy of excitons in quantum dots still remains open. In this work, by...
Article
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The optical spectra of films composed of spherical silicon-dioxide particles coated with small-radius CdS quantum dots are recorded and analyzed. Large shifts of the absorption and photoluminescence bands are detected and studied in relation to the concentration of quantum dots and to the pumping density and wavelength. Analysis of the experimental...
Article
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Topologically disordered films based on binary mixtures of SiO2 nanoparticles with CdS quantum dots on their surface with different surface and volume concentrations are studied. For the first time, a percolation transition of excitons has been observed in the CdS quantum dots array on a quasi-two-dimensional surface and the features of its formati...
Article
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Optical absorption spectra of colloidal solutions and films based on ZnSe quantum dots (QD) stabilized with thioglycerol or thioglycolic acid and precipitated on spherical nanoparticles of silica dioxide are presented and studied. In addition to the usual quantum-size effect another two contributions to the QD excitons energy were revealed. The fir...
Article
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The results of experimental studies of films fabricated on the basis of binary mixtures consisting of bare submicron silica particles (SPs) and silica particles covered with CdS quantum dots (NPs) are reported. The performed analysis concerns various coverage degrees and various SP-to-NP concentration ratios. By analyzing the sedimentation time and...
Article
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We report on a study of the absorption spectra and third-order nonlinear optical properties of crystalline PdO thin films, grown by oxidation of thin palladium films deposited on a substrate. The spectra reveal an absorption peak at λ=480nm, which grows and narrows significantly as the temperature is lowered to T=77K. This behavior suggests an exci...
Article
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The porous silicon (PS) surface modification diagnostics due to functionalization and water adsorption/desorption processes were provided by the self-action effects of picosecond range pulsed laser radiation at 1064 nm. It was shown that the PS surface functionalization - oxide removal, alkylation and oxidation - resulted in refractive nonlinear op...
Article
Spectral and nonlinear optical properties of mono- and multilayer films based on the gold multiprong nanostars are studied. As shown, the position of localized plasmon resonance (LPR) maximum varies in the range of 530-570 nm depending on the number of building-up cycles of monolayer films. As revealed for the multilayer films, the LPR band is expa...
Article
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The extinction spectra and the parameters of cubic optical nonlinearity in thin Fe2O3 and Cr2O3 films deposited on glass substrates with the use of the laser sputtering method have been measured. The cubic optical nonlinearity is studied, by using femtosecond laser radiation with the wavelength 𝜆 = 800 nm and the pulse duration 𝜏 = 180 fs. The ener...
Conference Paper
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The harmonic nanoparticles (HNPs) are unique, inherently nonlinear nanoparticles that are optically active exhibiting a strong and selective response (second/third harmonic) to nonlinear optical (NLO) excitation [1]. They increasingly applied as contrast agents for various imaging techniques. Considering the growing interest the express methods of...
Conference Paper
Full-text available
A novel composite system based on KDP single crystals with embedded nanoparticles (NPs) of nanostructured oxyhydroxide of aluminum (Al2O3∙nH2O, NOA) was grown. The optical characterization of the obtained material showed the high optical quality and homogeneity of the nanocompites. The zonal structure with a spatial period ~ 4 μm independent on the...
Article
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The problem of mathematical interpretation of experimental research results concerning the influence of incorporated TiO2 nanoparticles on the optical properties of the nonlinear optical material potassium dihydrogen phosphate has been formulated and solved, by using the computational physics methods. The mathematical model is reduced to a Fredholm...
Article
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The results of spectroscopic researches of porous and disordered films fabricated on the basis of spherical elements of the “core/shell” type, SiO2/CdS nanoparticles (SiO2 spheres covered with CdS quantum dots) are reported. The quantum-size effect of excitons in the quantum dots located on the surface of spheres is found to depend on the sphere si...
Article
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For the first time the diagnostics of oxyorthosilicates single crystals based on self-action of picosecond range laser pulses at 1064 nm (1.17 eV) has been performed. High sensitivity of the photoinduced refractive index variation to the substitution of the Lu atoms by Gd in the LSO/LGSO crystalline host as well as to the admixture of Ce was found....
Conference Paper
Full-text available
It is known that the incorporation of metal oxides (MO) nanoparticles (NPs) is a promising way to improve the nonlinear optical (NLO) properties of commercially used KDP crystals. Recently it was shown the significant improvement of the NLO response as well as the second harmonic (SH) and supercontinuum generation efficiency (up to 70 % at picoseco...
Chapter
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Recent improvements in powder synthesis and ceramics sintering made it possible to fabricate high-quality materials. Of particular interest to this work is the structural and optical characterization of (Y3Al5 O12 , YAG) ceramics fabricated by high-pressure low-temperature technique (HPLT). We study the effect of sintering temperature on structural...
Chapter
Full-text available
We have obtained the significant enhancement (up to 70 %) of the second harmonic generation efficiency in the novel composite material based on KDP single crystalline matrix with incorporated anatase nanoparticles under the mode-locked YAG:Nd laser pulses. The effect is explained by the internal self-focusing at moderate pump peak intensity due to...
Article
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Nonlinear optical response of Au island films to femtosecond laser pulses is studied in the vicinity but not exactly at the surface plasmon absorption peak (λ spr = 560 nm). The third-order nonlinear optical susceptibility is shown to be Reχ (3) = +1.7 × 10−7 esu and Reχ (3) = +1 × 10−7 esu at the wavelengths 800 and 460 nm, respectively. Kinetics...
Data
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Nonlinear optical response of Au island films to femtosecond laser pulses is studied in the vicinity but not exactly at the surface plasmon absorption peak (kspr = 560 nm). The third-order nonlinear optical susceptibility is shown to be Rev(3) = ?1.7 9 10-7 esu and Rev(3) = ?1 9 10-7 esu at the wavelengths 800 and 460 nm, respectively. Kinetics of...
Article
The second harmonic generation efficiency was studied for the single crystalline potassium dihydrogen phosphate matrix with incorporated TiO2 nanocrystals in the field of the mode-locked Nd:YAG laser pulses. For the first time the frequency conversion efficiency gain was observed for KDP:TiO2 single crystal (SC) instead of KDP SC due to the interna...
Article
The adaptive photo-EMF photodetectors, based on the measurement of the non-stationary holographic current in the CdTe:V crystals were elaborated using the interferometric scheme under excitation by the He-Ne laser (? = 1,15 ?k, P ? 1 mW). The characteristics of such photodetectors were established. The mechanism of the formation of the periodic spa...
Conference Paper
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Efficient impact of the incorporated metal oxides nanoparticles on self-action effects and optical harmonics generation was studied in single crystalline KDP matrix. It was shown possibility to enhance laser frequency conversion efficiency due to the anatase giant optical response manifestation.
Conference Paper
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Linear and nonlinear optical properties of pHEMA-oxo-TiO2 nanohybrids were studied. The reduction of refractive index with the increase of UV irradiation dose was observed. The TiO2 nanoparticles concentration strongly affects the nonlinear optical response of the composite system.
Article
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The results of studies of samples containing ZnSe quantum dots with a density corresponding to or considerably higher than the exciton percolation threshold, at which quantum dots form conglomerates, are reported. Excitonic emission from a percolation cluster of bound quantum dots as a fractal object is observed for the first time. Analysis of the...
Article
Nonlinear refraction in a new polymer material based on diglycidylether of bisphenol-A and containing 4-aminoazobenzene covalently attached to the polymer chains have been studied. The material was shown to exhibit fast nonlinear response (relaxation time about 20 ns, χ(3)= 5 × 10- 8 esu) together with slow one (relaxation time of the order of tens...
Article
Full-text available
The aim of this study is to investigate the nonlinearity of refraction in nanostructured silicon carbide films depending on their structural features (synthesis conditions for such films, substrate temperature during their deposition, concentration of the crystalline phase in the film, Si/C ratio of atomic concentrations in the film, and size of Si...
Article
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For the first time, the impact of TiO2 (anatase modification) nanocrystals on the photoinduced optical absorption and refractive index variations in KDP single crystals with the self-action of CW laser radiation at 532 and 1064 nm is studied. It is shown that the incorporation of anatase nanoparticles changes the sign of the refractive nonlinear op...
Article
Full-text available
Two-phase systems (borosilicate glass with ZnSe quantum dots) were studied. The results obtained provided an insight both into the mechanism of formation of a phase percolation transition of excitons in the array of quantum dots at the critical concentration and radii and the contribution of dielectric mismatch between ZnSe and matrix to the transi...
Article
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We study core/shell heterostructures in which a core (SiO2) is overcoated with a shell of ZnO quantum dots, randomly distributed on the sphere surface with the surface filling factor P∼0.45. Due to the high surface energy of SiO2 spheres, ZnO quantum dots have the shape of disks in which, in spite of the large radii, quantum size effects of exciton...
Article
Full-text available
Nonlinear optical properties of thin films of the organic merocyanine dye derived from the class of malonodinitrile dyes, as well as its solid guest-host systems based on polymethyl methacrylate are studied. The optical absorption spectra of films with different dye concentrations and of the dye solutions in non-polar solvents are measured. The sca...
Article
The impact of titanium dioxide (anatase) nanocrystals on growth process, optical and structural properties of KDP single crystal was studied. As-grown crystals were characterized by High Resolution Three-crystal X-ray Diffractometer, optical diagnostics of elastic scattering, cone-shaped interference method, and spatial profile analysis method. In...
Article
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We study the elastic scattering of light in pure KDP crystals and KDP crystals with incorporated titanium dioxide nanoparticles. It is shown that the optical quality of the crystals decreases insufficiently for the used concentrations of nanoparticles. A mathematical model of the experimental setup for light scattering measurements in low-dispersio...
Article
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From studies of two-phase systems (borosilicate matrices containing ZnSe or CdS quantum dots), it was found that the systems exhibit a specific feature associated with the percolation phase transition of charge carriers (excitons). The transition manifests itself as radical changes in the optical spectra of both ZnSe and CdS quantum dot systems and...
Article
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We report the results of studies of two-phase core-shell (SiO2/ZnO) structures with a large density of ZnO nanoclusters on the surface of spherical SiO2 nanoparticles. It is proved that, due to the large surface energy of the latter, nanoclusters grow in the form of quantum disks with diameter exceeding 10 nm and with height of the order of the Boh...
Article
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Using microscopy techniques of femtosecond time-resolved optical polarigraphy and transient absorption, we have demonstrated reshaping of a filamented laser pulse propagating within the bulk of fused silica caused by expulsion of light from the plasma-occupied core area. Transformation of the axially symmetric pulse shape into an asymmetric double-...
Article
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This report concentrates on dynamic probabilistic risk analysis of optical elements for complex characterization of damages using physical model of solid state lasers and predictable level of ionizing radiation and space weather. The following main subjects will be covered by our report: (a) a solid-state laser model; (b) mathematical models for dy...
Article
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The results of our researches of borosilicate glasses with CdS quantum dots (QDs), the dimensions of which are smaller than the exciton Bohr radius, are reported. The mean size of quantum dots for a given CdS concentration has been calculated in the effective mass approximation, the result obtained being in good agreement with X-ray data. In the sa...
Article
Full-text available
Nonlinear refraction in nanocrystalline SiC films, which have been obtained using the method of direct deposition of carbon and silicon ions with an energy of 100 eV at substrate temperatures from 900 to 1150°C, has been investigated. It has been shown that the films exhibit a large third-order nonlinear susceptibility χ (3) ∼ 10−6 esu (at λ = 1064...
Article
Full-text available
Nonlinear refraction has been for the first time studied in silicon carbide nanocrystal films synthesized by new technique of direct carbide and silicon ion deposition with ion energy of 100eV and low substrate temperature from 900°C to 1150°C. The films were shown to exhibit large optical nonlinear cubic susceptibility chi(3) ≅ 10-6 esu (lambda=10...
Article
Full-text available
Giant nonlinear refraction has been experimentally observed in gold island films. The complex third-order nonlinear susceptibility chi(3)(omegaomega,-omega,omega) reaches a value of -8×10-5 esu (lambda = 532 nm, iota = 10 ns) and (+5×10-7 + i0.3×10-7) esu (lambda = 800 nm, iota = 85 fs). The mechanism of nonlinearity of the refractive index can be...
Article
Giant nonlinear refraction has been experimentally observed in gold island films. The real part of the third-order nonlinear susceptibility χ(3)(ωω,-ω,ω) reaches a value of -8×10-5 esu (λ = 532 nm, τ = 10 ns) and +5×10-7 esu (λ = 800 nm, τ = 85 fs). The mechanism of nonlinearity of the refractive index can be associated with the resonance enhanceme...
Article
Full-text available
Summary form only given. Silicon carbide nanocrystal films have been synthesized by new original technique of direct ion deposition. Composition and structure of bonds between carbon and silicon atoms have been studied by means of photo-electron spectroscopy using XPS-800 Kratos spectrometer with MgK radiation. The spectra have been calibrated usin...
Article
Full-text available
The optical spectra of quantum dots of CdS and ZnSe grown in borosilicate glass by the sol-gel method are obtained and analyzed. It is found that at concentrations of the two semiconductors x0.06%. The emission from the surface level of CdS QDs in the region ~2.7 eV, formed by the outer atoms with dangling bonds, is observed for the first time, as...
Article
The optical spectra from quantum dots of CdS and ZnSe grown by the sol-gel method in borosilicate glass are taken and analyzed. It is found that for the both semiconductors with x < 0.06% the radiation spectra are conditioned by the annihilation of free (internal) exitons in the quantum states. For that concentration, calculated is the mean size of...
Article
It is shown that in laser experiments performed by using an 'imperfect' setup when instrumental distortions are considerable, sufficiently accurate results can be obtained by the modern methods of computational physics. It is found for the first time that a new instrumental function — the 'cap' function — a 'sister' of a Gaussian curve proved to be...
Article
Both scalar and vector gratings were recorded in an epoxy-based polymer with 4-amino-azobenzene depending on the geometry of the recording by the second harmonic of a pulsed Nd:YAG laser. A new mechanism of nonlinear refraction (striction) is suggested and is experimentally observed for the first time in the medium under study.
Article
We have synthesized a composite material containing semiconductor nanocrystals with a high third-order optical nonlinear susceptibility χ (ω) = (6.5±2.3) · 10 m/V (PbS-18 nm) at λ = 1.064 nm in the case where the nanocrystal size approaches the Bohr radius of an exciton in the material.
Article
Full-text available
For the first time photo-electromotive force (photo-EMF) measurements were carried out for CdTe crystals doped with V atoms as a result of the photogeneration of carriers from deep impurity centers to the conduction band. Tilted geometry was applied that allowed two-dimensional monitoring of the vi- bration source. The CdTe:V crystals were excited...
Article
For the first time photo-electromotive force (photo-EMF) measurements were carried out for CdTe crystals doped with V atoms as a result of the photogeneration of carriers from deep impurity centers to the conduction band. Tilted geometry was applied that allowed two-dimensional monitoring of the vi- bration source. The CdTe:V crystals were excited...
Article
The complex investigation of the cyanine bases, containing benzo[c,d]indole as residue group was carried out by linear and non-linear optical spectroscopic and quantum-chemical modelling methods. It was found that non-linear optical properties were more sensitive to the nature of the varied donor terminal group than the absorption spectra; the incr...
Article
Full-text available
For the first time the photo-EMF measurements were carried out for CdTe crystals doped with V atoms as a result of the photogeneration of carriers from deep impurity centers to the conduction band and the tilted geometry was applied that allowed two-mentional monitoring of the vibration source. The CdTe:V crystals were excited by a He-Ne laser with...
Article
Full-text available
The photoluminescence spectra of CdS quantum dots grown in a borosilicate glass by sol-gel technology are recorded and analyzed. It is shown that the photoluminescence spectra of the samples are related to annihilation of free (interior) excitons in the ground state and excited state. Emission associated with the surface states of the quantum dots...
Article
Full-text available
The complex investigation of the cyanine bases, containing benzo[c,d]indole as residue group was carried out by linear and non-linear optical spectroscopic and quantum-chemical modelling methods. It was found that non-linear optical properties were more sensitive to the nature of the varied donor terminal group than the absorption spectra; the incr...
Article
Full-text available
Laser chemical vapor deposition (LCVD) method based on Ar+ laser radiation was applied for the synthesis of nanometric structures based on iron oxides Fe2O3-X (0 <= x <= 1) in the form of thin films. These structures were formed while deposition of elements from iron carbonyl vapors (Fe(CO)(5)). The thickness of deposited films was no more than 30...
Article
Full-text available
A giant nonlinear optical response has been observed for nanoporous layers of titanium dioxide (anatase) under picosecond laser excitation with photon energy below the gap. At excitation intensity of 10 MW/cm2 the nonlinear refractive index variation at the wavelength of 1064 nm corresponds to χ(3)=2×10-5 esu which is six orders of magnitude higher...
Article
Photoinduced anisotropy and vector holographic recording by pulsed (10 ns) 532 nm laser radiation have been studied in a polymer based on bisphenol-A diglycydyl ether with 4-aminiazobenzene molecules covalently attached to the polymer chain. It is shown that nonlinear refraction in the time range from microseconds to several hours in the polymer is...
Article
Giant nonlinear optical response has been observed for nanoparticle TiO2 (anatase modification) layers within sub-gap photon energy excitation in picosecond range. The obtained effective cubic optical nonlinearity value χ(3)eff ∼10–5 esu is six orders of magnitude higher than the bulk response in transparency range. The effect can be explained with...
Conference Paper
Full-text available
Nanocrystalline TiO 2 is one of the most being investigated semiconductor materials with unique physical and chemical properties. The reason of its popularity is the wide range of its applications and the expectation that insight into surface properties on the fundamental level will help to improve materials and devices performance in many fields (...
Conference Paper
Full-text available
Laser chemical vapor deposition (LCVD) method was applied for synthesizing of nanometric structures based on iron oxides Fe 2 O 3-X (0≤x≤1) in form of thin films. These structures were formed while deposition of elements from iron carbonyl vapors (Fe(CO) 5). Iron oxides were formed owing to oxidizing process of atomic iron with atomic oxygen to hav...
Article
High third-order nonlinear optical susceptibility (χ(ω; ω, −ω, ω) = −4,2 × 10(m/V)). In the visible spectral range may be achieved in PVA composites containing narrow bad gap PbS semiconductor nanocrystals with a strong limitation of the area of charge carrier delocalization.
Article
Full-text available
We have examined the efficiency of various techniques for the determination of the nonlinear optical response (NLO) of dye-doped liquid crystals. The intensity ranges where each technique is optimal are defined. We propose an approach for precise and detailed NLO response measurements as a function of dye concentration when the optical parameters o...
Article
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The paper presents the results of the complex investigation of linear and nonlinear parameters of new organic compound type - polymethine dye base (PDB) - 1-pentafluorophenyl-4-phenyl-5,6,7,8-tetrahydro-8-[(4-dimethylaminophenyl)methylene]-quinoline. For the first time thin films on glass substrate from this material were deposited by physical evap...