Dmitry I. Staselko

Femtosecond stimulated Raman scattering in pressurized gases in the ultraviolet and visible spectral ranges

We investigate femtosecond stimulated Raman scattering (SRS) in H2,D2, HD, and CH4 excited with 300-fs-duration pulses at 390-nm wavelength and with as much as 0.1 mJ of energy. We show that the SRS-generation threshold and conversion efficiency are due to the transient nature of SRS in femtosecond regime. We determine optimal conditions for efficient generation in the broad spectral range 289–797 nm and show how self-phase modulation and white-light generation limit the ultimate conversion efficiency.

Stimulated Raman scattering in hydrogen by frequency-doubled amplified femtosecond Ti:sapphire laser pulses

We present results on stimulated Raman scattering in hydrogen excited by 200-fs-duration 1-kHz repetitionrate and 0.6-W average-power Ti:sapphire (780-nm) and 0.2-W average-power second-harmonic (390-nm) laser pulses with linear and circular polarizations. Spectral and temporal measurements of the vibrational and rotational components at Stokes and anti-Stokes frequencies in the wavelength range of 289-1154 nm are reported. We observe threefold shortening of the first vibrational Stokes component pulses, excited by 400-fsduration second-harmonic pulses.

Stimulated Raman amplification of femtosecond pulses in hydrogen gas.

We report efficient amplification of weak femtosecond supercontinuum pulses by a stimulated Raman scattering process in pressurized H(2) gas excited with 350-fs-duration frequency-doubled pulses from a regenerativeamplified Ti:sapphire laser. An amplification factor of 10(9) is obtained at the wavelength of 465 nm for seed pulses produced by supercontinuum generation in glass.

Transient stimulated Raman scattering in gas mixtures.

We studied, for the first time to our knowledge, transient stimulated Raman scattering in H(2)- D(2) and H(2)- CH(4) gas mixtures excited with 200-fs and 2-ps, 390-nm pulses. Depending on the composition and partial pressure, of those gases, we observed approximately 40 output lines simultaneously. Under optimum conditions a conversion efficiency of as much as 8% in the combination Raman line at 556 nm was obtained in the H(2)- CH(4) gas mixtures. The difference between picosecond and femtosecond pumping is due to self-phase modulation and to generation of a spectral continuum in the latter. Our calculation of the ratio of the partial pressures is in a good agreement with the experimental results. A new method for measuring the unknown Raman scattering cross section of gas molecules is suggested.

Holographic recording in thin C70-doped polymer organic films

Abstract The dynamic and static thin holographic gratings have been recorded in C 70 -doped photosensitive polyimide 6B and 2-cyclooctylamino-5-nitropyridine. The drastic change in diffraction efficiency has been observed under the Raman–Nath diffraction condition using the second harmonic of pulse Nd laser. The threshold of the transition from phase grating to amplitude one has been determined. The results obtained have been explained by the absorption spectral peculiarities of the fullerene-doped films and by their thermal properties.

Fullerene-doped polymer-dispersed liquid crystals: holographic recording and optical limiting effect

In the fullerene-doped polymer dispersed liquid crystals the holographic recording and optical limiting effect have been established to be intermediate between those for fullerene- doped liquid crystals and for fullerene-doped polymers. It has been shown that fullerene-doped polymer-dispersed liquid crystals could be applied for optical limiting at the incident laser power of 0-3-0.4 J cm-2. They can be used as effective diffractive optical elements.

Degenerate four-wave mixing by nonlinear resonant reflection of radiation from cesium vapor boundary

Results of experimental investigation of degenerate four-wave mixing by resonant reflection of single-frequency cw-semiconductor laser radiation from sapphire-cesium vapor boundary are presented. It is shown that characteristics of such mixing are conditioned by the peculiarities of formation and washing out of reflection dynamic gratings in a thin atomic layer

Second-order nonlinearity of the material for recording holograms in the case when frequencies of object and reference waves are different

The transformation properties of dynamic hologram recorded in a quadratically nonlinear material are considered for the general case when the frequencies of object and reference waves are essentially different. The expressions are deduced that determined the wavelength of the reconstructed wave and directions of propagation of the rays of light that form the image. An experiment is carried out on the base of a noncollinear scheme of nonlinear interaction. A hologram was recorded in a KTP crystal by the light of a YAG:Nd laser (λ = 1.064 μm), the width of the pulses being 300 ps. The frequency of the object wave was shifted due to the Raman scattering in a crystal Ba(NO3)2. The values of the frequency shifts were Δν, 2Δν, 3Δν (Δν = 1047 cm-1). Each of the shifted in frequency component formed an image of the object whose resolution was close to the diffraction limit. All these components were separated in space. The value of separation was in a good agreement with the predictions of the theory. It was stressed that the inertialess nature of a hologram of such a type makes it possible to use them for ultrafast communication of signals in optical communication lines.

Increasing THz generation from InAs surface using a compact permanent magnet system

In this paper the authors report the investigation of terahertz generation from an InAs surface, exposed to a strong magnetic field and pumped by a femtosecond optical pulse.

χ(2)-holographic instantaneous image formation using multifrequency object and reference beams

Some new results of experimental study of multifrequency χ(2)-dynamic hologram image formation are presented. The main distinguishing feature of our experiments was the use not only of a multifrequency object wave but a multifrequency reference one, too. As a result, we have simultaneously observed at the same wavelength (λ=564 nm) two frequency summing holographic images formed by nonlinear crystal KTP and arranged nearly symmetrically around SHG image (λ=432 nm) both in transverse and longitudinal directions according to the theoretical treatment. These images can be used for noninertial optical channels switching and addressing with change of wavelength and spatial localization of images including the information.