V. Slabko - Academia.edu (original) (raw)

Papers by V. Slabko

2016 International Conference Laser Optics (LO), 2016

Based on the theory of the optical properties of fractal clusters, which is an operator-based mod... more Based on the theory of the optical properties of fractal clusters, which is an operator-based modification of the coupled-dipole method, an alternate solution is proposed for the problem of adequately describing the evolution of optical spectra of any polydisperse silver colloid with particles falling within the range of most characteristic sizes (5 − 30 nm). This is the range over which the results of the application of the well-known methods of classical electrodynamics, including the Mie theory, disagree with experimental data. The effect of variation of the parameters of such media on optical spectra is studied by a numerical simulation, which accounts for particle electrodynamic dipole-dipole interactions. Indeed, such interactions are shown to be a key factor in determining the broadening of the sol absorption spectra during the course of fractal aggregation. A quantitative explanation is given for the reasons for the appearance of individual specific features in the contours of the spectral absorption of different types of silver colloids.

Nonlinear Optics and Applications V, 2011

ABSTRACT The properties of NPC structures in strontium tetraborate are analyzed. Different types ... more ABSTRACT The properties of NPC structures in strontium tetraborate are analyzed. Different types of NPC structures are revealed that possess different nonlinear properties, and their spectral dependences of frequency conversion efficiency are calculated and compared. Experimental study of these structures is reported for the process of doubling of the second harmonic of fs Ti:S laser. Tuning of generated radiation is obtained in the range 187.5 - 232.5 nm, with extreme insensitivity to the angular orientation of NPC. Behavior of tuning curve along investigated fundamental wave range is similar in all studied samples, but efficiency obtained depends on the type of structure. Conversion efficiency andspectral quality of generated radiation is experimentally shown to grow better when using NPC with improved structure. Prospects of VUV converter on a single NPC are discussed. NPCs of SBO are demonstrated to be useful for autocorrelation diagnostics both in random QPM geometry and in the geometry of nonlinear diffraction from virtual beam.

Soviet Journal of Quantum Electronics, 1988

ABSTRACT The results are given of theoretical and experimental investigations of the generation o... more ABSTRACT The results are given of theoretical and experimental investigations of the generation of vacuum ultraviolet radiation by parametric frequency mixing of radiation from a neodymium laser using higher nonlinearities of a mercury vapor. The effects of interference of nonlinear polarizations of the seventh nonresonant and ninth resonant orders are reported. Investigations of the frequency dependence of the breakdown threshold (which is the main limiting factor) make it possible to relate the reduction in the threshold to a change from ten- to nine-photon ionization.

Soviet Journal of Quantum Electronics, 1986

An investigation was made of the feasibility of eliminating constraints imposed by nonlinear refr... more An investigation was made of the feasibility of eliminating constraints imposed by nonlinear refraction on the maximum attainable conversion efficiency for third harmonic generation (THG) in centrosymmetric gaseous media. A numerical analysis of reduced equations showed that if cw pump radiation is focused beyond the nonlinear medium, the THG efficiency may reach values close to unity in spite of appreciable

Inorganic Materials, 2005

Data are presented on the phase composition, particle size distribution, EPR, and luminescence of... more Data are presented on the phase composition, particle size distribution, EPR, and luminescence of ultrafine chromium-doped alumina powders prepared by detonation synthesis. The largest particles in the powders are shown to consist mainly of a Cr 2 O 3 solid solution in α -Al 2 O 3 . The luminescence spectrum of fine particles shows, in addition to lines characteristic of ruby, extra lines which are tentatively attributed to Cr 3+ ions incorporated substitutionally into θ -Al 2 O 3 .

Physical mechanisms of the reasons for dramatic (up to 10 8 times) acceleration of the aggregatio... more Physical mechanisms of the reasons for dramatic (up to 10 8 times) acceleration of the aggregation of sol metals under the action of light are proposed for the first time. These mechanisms were classified with allowance for the procedure of sol stabilization and type of dispersion medium; their comparative analysis was performed using the main types of silver sols as the most convenient model medium. Mechanisms proposed are based on the current notions of the theory of coagulation kinetics and stability of sols with account of interfacial processes, as well as of the theory of photoeffect corrected for the influence of dispersion medium and the amplification of local electromagnetic fields inherent in colloidal structures with fractal geometry.

Micro- and Nanotechnology Sensors, Systems, and Applications V, 2013

A concept of a family of unique backward-wave photonic devices, such as frequency up and down con... more A concept of a family of unique backward-wave photonic devices, such as frequency up and down converting nonlinear-optical mirrors, sensors, modulators, filters and amplifiers is proposed. Novel materials are considered, which support coexistence of ordinary and backward waves and thus enable enhanced nonlinear-optical frequency-conversion processes. Particular properties of short-pulse regime are investigated.

Solid State Phenomena, 2014

ABSTRACT Extraordinary properties of nonlinear-optical propagation processes are investigated tha... more ABSTRACT Extraordinary properties of nonlinear-optical propagation processes are investigated that involve electromagnetic or elastic waves with negative group velocity. Nanostructured materials that support such waves and prospective unique photonic devices are described.

Soviet Journal of Quantum Electronics, 1992

Parametric lasing in the vacuum-ultraviolet range was investigated experimentally in barium vapor... more Parametric lasing in the vacuum-ultraviolet range was investigated experimentally in barium vapor. Picosecond YAlO3:Nd3+ laser pulses were frequency-converted to the ∼ 180-nm range with an efficiency of 0.7%. The dependences of the conversion efficiency on the buffer gas pressure and on the position of the constriction of the pump radiation beam were studied. The principal factor limiting the efficiency under resonance conditions was found to be the Stark effect.

$Research paper thumbnail of Nonlinear Raman–Nath diffraction of femtosecond laser pulses$

We study the nonlinear Raman-Nath diffraction (NRND) of femtosecond laser pulses in a 1D periodic... more We study the nonlinear Raman-Nath diffraction (NRND) of femtosecond laser pulses in a 1D periodic nonlinear photonic structure. The calculated second-harmonic spectra represent frequency combs for different orders of transverse phase matching. These frequency combs are in close analogy with the well-known spectral Maker fringes observed in single crystals. The spectral intensity of the second harmonic experiences a redshift with a propagation angle, which is opposite the case ofČerenkov nonlinear diffraction. We analyze how NRND is affected by the groupvelocity mismatch between fundamental and second-harmonic pulses and by the parameters of the structure. Our experimental results prove the theoretical predictions.

Strontium tetraborate (SBO) possesses transparency in the VUV that allows nonlinear generaton to ... more Strontium tetraborate (SBO) possesses transparency in the VUV that allows nonlinear generaton to the wavelengths as short as 125 nm. The existence of domain structures consisting of alternating oppositely poled domains is found in as grown crystals of SBO. Domain walls are perpendicular to a crystallographic axis. In this paper non-collinear generation (nonlinear diffraction) of the second and third harmonics of nanosecond Nd:YAG laser is used for the investigation of reciprocal superlattice vectors (RSV) spectrum of the domain structures. When fundamental radiation propagates in the vicinity of direction perpendicular to the domain walls, random quasi phase matching (RQPM) was observed in the process of generation of 266 nm radiation via doubling of the second harmonic of nanosecond Nd:YAG laser. Maximum efficiency of conversion is 0.5% and exceeds that obtained for 2D nonlinear photonic crystal based on strontium barium niobate.

$Research paper thumbnail of Laser-induced formation of fractal structures in silver colloids and its spectroscopic appearing$

Fundamentals of Laser-Matter Interaction: Icono '95, 1996

ABSTRACT

$Research paper thumbnail of Optical spectra of silver colloids within the framework of fractal physics$

Colloid Journal, 2000

Based on the theory of the optical properties of fractal clusters, an alternate solution to the p... more Based on the theory of the optical properties of fractal clusters, an alternate solution to the problem of adequately describing the evolution of optical spectra of any polydisperse silver colloids with particles falling within a range of most characteristic sizes (5-30 nm), over which the results of the application of the methods of classical electrodynamics including the Mie theory, disagree with experimental data, was proposed. The effect of various parameters of such media on optical spectra was studied by a mathematical simulation with allowance for particle electrodynamic interaction. An obvious quantitative explanation is given for the reasons for the appearance of individual specific features in contours of the spectral absorption of different-type silver colloids.

A powerful frequency-tunable neodymium glass laser active mode-locked laser system is described. ... more A powerful frequency-tunable neodymium glass laser active mode-locked laser system is described. Near-complete mode locking is provided by periodic Q-modulation of the resonator in combination with spectral selection of longitudinal types of oscillation. Preliminary findings from experiments in generating the seventh harmonic in mercury vapor are cited. The output parameters of the laser satisfy the conditions for experiments on generating higher harmonics of the fundamental radiation. The pulse length of the periodic Q-modulated laser is independent of the spectrum width of the radiation generated in the band extending from several tens to several tenths of a centimeter. The periodic Q-modulation scheme can be used for active mode locking.

Technical Physics Letters, 2001

An ultradisperse alumina (Al2O3) powder doped with Cr3+ ions was synthesized for the first time b... more An ultradisperse alumina (Al2O3) powder doped with Cr3+ ions was synthesized for the first time by shock-wave loading of a mixture of aluminum powder and ammonium chromate. The synthesized powder is composed primarily of the chromium-doped α-and δ-Al2O3 particles. The luminescence spectra of the α phase are identical to those of a macroscopic ruby crystal sample, which indicates that chromium

$Research paper thumbnail of Photochromic reactions in silver nanocomposites with a fractal structure and their comparative characteristics$

Technical Physics, 2003

Conditions for a change in the polarization selectivity of dips in the plasmon absorption spectra... more Conditions for a change in the polarization selectivity of dips in the plasmon absorption spectra of fractal silver nanocomposites irradiated by pulsed laser radiation are studied. The energy thresholds of the polarization selectivity are evaluated, and the polarization and spectral threshold characteristics are compared. Mechanisms behind a correlation between the fractal structure of the nanocomposites, on the one hand, and their optical and photochromic properties, on the other hand, are discussed. © 2003 MAIK "Nauka/Interperiodica".