arXiv subjects

O. A. Aktsipetrov

Publications and source records attributed to O. A. Aktsipetrov.

10 recordsLinked to original sources

arXiv2007

Current-induced break of inversion symmetry in Si: optical second-harmonic generation induced by a dc current

The dc-current-induced optical second-harmonic generation is observed at the surface of centrosymmetric single crystal of Si. Surface dc-current with density up to $\textit{j}_{max} \sim 10^{3}$ A/cm$^{2}$ results in break of inversion symmetry of Si and induces optical second-harmonic generation with intensity that corresponds to the appearance of dipole second-order susceptibility $χ^{(2)d}(j_{max})\sim 3 \cdot 10^{-15}$m/V.

physics.optics↗

arXiv2006

Magnetization-induced optical second-harmonic generation and local surface plasmons in magnetic $Co_x Ag_{1-x}$ nanogranular films

Spectroscopy of magnetization-induced second-harmonic generation (MSHG) is studied in magnetic Co$_{x}$Ag$_{1-x}$ granular films containing Co nanoparticles. A strong resonance of the magnetic contrast of the second-harmonic generation (SHG) intensity is observed in the two-photon energy range from 3,8 eV to 4,5 eV. The local surface plasmons exited in magnetic Co nanogranules in this spectral range assist MSHG and are responsible for a significant enhancement of the SHG magnetic contrast due to the resonances of local optical fields.

nlin.AO↗

arXiv2005

Surface-enhanced optical third-harmonic generation in Ag island films

Surface-enhanced optical third-harmonic generation (THG) is observed in silver island films. The THG intensity from Ag nanoparticles is enhanced by more than two orders of magnitude with respect to the THG intensity from a smooth and homogeneous silver surface. This enhancement is attributed to local plasmon excitation and resonance of the local field at the third-harmonic wavelength. The diffuse and depolarized component of the enhanced THG is associated with the third-order hyper-Rayleigh scattering in a 2-D random array of silver nanoparticles.

cond-mat.other↗

arXiv2004

Magnetization-induced optical third-harmonic generation in Co and Fe nanostructures

Magnetization-induced optical third-harmonic generation (MTHG) is observed in magnetic nanostructures: Co and Fe nanolayers and granular films containing Co nanoparticles. Magnetization-induced variations of the MTHG characteristics in these nanostructures exceed the typical values of linear magneto-optical Kerr effect by at least an order of magnitude: the maximum of magnetic contrast in the MTHG intensity is up to 0.2, the angle of polarization rotation for MTHG is 10 deg. and the relative phase shift is up to 100 deg.

cond-mat.mtrl-sci↗

arXiv2003

Ferroelectric ordering and electroclinic effect in chiral smectic liquid crystals

Ferroelectric ordering, the electroclinic effect and chiral smectic C (SmC*) - smectic A (SmA*) phase transitions in thin planar ferroelectric liquid crystal (FLC) cells are studied by means of linear electrooptic and second harmonic generation techniques. The ferroelectric switching is detected in biased FLC cells by measuring azimuthal dependences of linear and nonlinear responses. The applied DC-electric field rotates the FLC symmetry axis with initial and final orientations in the cell plane. Comparative studies of the switching behavior in reflection and transmission allows to distinguish the contributions from the bulk and the sub-surface layers of the cell. The analysis of temperature dependence shows the existence of a strong surface coupling. The temperature dependent nonlinear polarization shows a critical behavior corresponding to the superfluid model.

physics.optics↗

arXiv2000

Second-harmonic interferometric spectroscopy of the buried Si(111)-SiO$_2$ interface

The second-harmonic interferometric spectroscopy (SHIS) which combines both amplitude (intensity) and phase spectra of the second-harmonic (SH) radiation is proposed as a new spectroscopic technique being sensitive to the type of critical points (CP's) of combined density of states at semiconductor surfaces. The increased sensitivity of SHIS technique is demonstrated for the buried Si(111)-SiO$_2$ interface for SH photon energies from 3.6 eV to 5 eV and allows to separate the resonant contributions from $E^\prime_0/E_1$, $E_2$ and $E^\prime_1$ CP's of silicon.

physics.optics↗

arXiv1999

Optical second harmonic generation probe of two-dimensional ferroelectricity

Optical second harmonic generation (SHG) is used as a noninvasive probe of two-dimensional (2D) ferroelectricity in Langmuir-Blodgett (LB) films of copolymer vinylidene fluoride with trifluorethylene. The surface 2D ferroelectric-paraelectric phase transition in the topmost layer of LB films and a thickness independent (almost 2D) transition in the bulk of these films are observed in temperature studies of SHG.

physics.optics↗

arXiv1999

Oscillatory screening of the dc electric field in the Si-SiO$_2$ multiple quantum wells probed by second-harmonic generation

DC-electric field, being screened in 3D semiconductors, normally decays monotonically in space. Experimental studies of the DC electric field screening in Si-SiO$_2$ multiple quantum wells by electric field induced optical second-harmonic generation show a non-monotonic, oscillatory-like decay. The model of electrons localized inside quantum wells, with the first subband occupied, allows a description of the phenomenon. Interwell Coulomb interaction, a finite value of the electron charge and strong effective-mass anisotropy result in a crucial difference from 3D Fermi liquid.

cond-mat↗

arXiv1999

Interferometry of hyper-Rayleigh scattering by inhomogeneous thin films

The use of specific symmetry properties of the optical second-harmonic generation (the s,s-exclusion rule) has allowed us to observe high-contrast hyper-Rayleigh interference patterns in a completely diffuse light - an effect having no analog in case of linear (Rayleigh) scattering.

physics.optics↗

arXiv1998

DC-electric-field-induced and low-frequency electromodulation second-harmonic generation spectroscopy of Si(001)-SiO$_2$ interfaces

The mechanism of DC-Electric-Field-Induced Second-Harmonic (EFISH) generation at weakly nonlinear buried Si(001)-SiO$_2$ interfaces is studied experimentally in planar Si(001)-SiO$_2$-Cr MOS structures by optical second-harmonic generation (SHG) spectroscopy with a tunable Ti:sapphire femtosecond laser. The spectral dependence of the EFISH contribution near the direct two-photon $E_1$ transition of silicon is extracted. A systematic phenomenological model of the EFISH phenomenon, including a detailed description of the space charge region (SCR) at the semiconductor-dielectric interface in accumulation, depletion, and inversion regimes, has been developed. The influence of surface quantization effects, interface states, charge traps in the oxide layer, doping concentration and oxide thickness on nonlocal screening of the DC-electric field and on breaking of inversion symmetry in the SCR is considered. The model describes EFISH generation in the SCR using a Green function formalism which takes into account all retardation and absorption effects of the fundamental and second harmonic (SH) waves, optical interference between field-dependent and field-independent contributions to the SH field and multiple reflection interference in the SiO$_2$ layer. Good agreement between the phenomenological model and our recent and new EFISH spectroscopic results is demonstrated. Finally, low-frequency electromodulated EFISH is demonstrated as a useful differential spectroscopic technique for studies of the Si-SiO$_2$ interface in silicon-based MOS structures.

physics.optics↗