I. A. Ozheredov

Enhancement of second-harmonic generation with femtosecond laser pulses near the photonic band edge for different polarizations of incident light

We present experimental evidence of enhancement of second-harmonic generation as a result of an increase of the fundamental-field energy density within a multilayer structure near the photonic band edge.

Four-wave mixing in one-dimensional photonic crystals: inhomogeneous-wave excitation

We present what is to our knowledge the first study of nonlinear four-wave mixing in one-dimensional photonic crystals. The possibility of inhomogeneous-wave excitation at the four-wave mixing frequency ω3=2ω1-ω2 for two noncollinear beams of femtosecond laser pulses is demonstrated. As a result of this effect the wave at the frequency of four-wave mixing may be guided along the surface of the photonic crystal. Experiments of this type open the possibility of development of a new tool based on photonic crystal devices for coherent Raman spectroscopy of surfaces and of nanometer and submicrometer scale layers.

Nonlinear process in photonic crystals under the noncollinear interaction

We analyzed theoretically and studied experimentally the sum-frequency generation and four-wave-mixing processes under the noncollinear geometry of interaction in finite-length periodic photonic crystals. The efficiency of the surface and the bulk mechanisms of sum-frequency generation are compared. It is shown that surface and bulk mechanisms cannot be separated on the polarization of the sum-frequency signal only but that the angular dependencies of the sum-frequency signal intensity enable us to separate them. The excitation of inhomogeneous waves at the four-wave-mixing frequency of ω3=2ω1-ω2 is discussed and demonstrated.

Interaction of High-Intensity Femtosecond Radiation With Gas Cluster Beam: Effect of Pulse Duration on Joint Terahertz and X-Ray Emission

This paper studies the phenomenon of joint generation of terahertz (THz) and X-ray radiation in the argon nanocluster jet under the action of high-power femtosecond laser pulse in both the single-color and dual-color regimes. It was discovered that in a gas cluster beam the pulse duration affects the properties of THz and X-ray emission differently. For the same given total energy of optical pulse in the dual-color excitation regime of cluster medium, more than a five times increase of THz radiation power was observed in comparison with the single-color regime, while the conversion efficiency to the argon X-ray K-line reached 7 × 10-6 and remained unchanged. The possibility of separation of contributions of different beam components into the THz signal was demonstrated experimentally, using contributions from clusters and nonclustered gas as an example. We suggest an interpretation of experimental results based on a theoretical model of cluster ionization that self-consistently predicts the level and dynamics of ionization and electron temperature in the clusters.

Formation of polymer films containing multivalent metal cations by stepwise alternate adsorption of metal cations and polyanions

Abstract Self-assembled multilayer films, in which molecular polyelectrolyte building blocks are held together by complexed multivalent metal cations, were prepared successfully via sequential layer-by-layer adsorption reactions. To form such films, rare-earth cations (Gd3+, Er3+, Nd3+), and poly(styrene sulfonate)-Na were used. The characterization of mutilayer built-up films, formed on the oxidized silicon and quartz substrates was carried out by atomic force microscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, X-ray diffraction. Gadolinium content in the material and magnetic properties of Gd-containing films were characterized by electron paramagnetic resonance technique. The data obtained indicate closely packed and homogeneous structure of built-up films with high content of rare-earth cations. Simple layer-by layer film growth procedure in this method, allows for the systematic effective nanometer-scale level single-layer control of chemical content, composition, functionality, metal cation complexes structure and film thickness. This structure, in turn, determines film properties of interest (optical, electronic, chemical, mechanical, magnetic etc.). As a result, such polymer rare-earth-doped film materials can be perspective for various photonic and other applications.

Generation of the second harmonic of femtosecond pulses on reflection from a metal surface: amplification due to periodic modulation of the relief

It is observed experimentally that the optical second-harmonic generation signal produced when femtosecond laser pulses are reflected from a metal surface increases more than 100-fold when a specially chosen periodic relief that gives quasiresonance excitation of a surface electro-magnetic wave is depoited on the surface.

Orienting Influence of Femtosecond Pulses on Nematic Liquid Crystals

ABSTRACT Orienting influence of femtosecond laser pulses on nematic liquid crystals has been studied. We have shown experimentally that in both a nematic liquid crystal doped with anthraquinone dye D4 and nematic matrix “mixture A” (consisting of azoxymolecules) the efficiency of the liquid-crystal director reorientation under the influence of femtosecond pulses is less than for continuous wave radiation. The mechanism responsible for this difference is associated with light-induced variation of the anchoring conditions.

Light-induced director reorientation in nematic liquid crystal under femtosecond pulses

The interaction of a nematic liquid crystal (NLC) with the succession of the femtosecond light pulses has been investigated. Direct experimental comparison between the nonlinear NLC response to femtosecond and cw radiation was performed.

Femtosecond optical pulse compression in a one-dimensional thin photonic crystal

The effect of femtosecond laser pulse compression is discovered, described, and experimentally studied for a one-dimensional 4.8-μm-thick photonic crystal.

Amplification of the generation of the sum-frequency signal in multilayer periodic structures at the edges of the Bragg band gap

A new property of a one-dimensional periodic structure — amplification of the sum-frequency signal arising under the simultaneous action of two laser pulses on this structure with radiation frequencies corresponding to the edges of the fixed Bragg band gap — is experimentally observed and described.