Alexander P. Tarasevitch

Parametric generation of high-peak-power femtosecond light pulses in LBO crystal

The parametric down conversion of femtosecond pulses at high intensity is discussed. An injection-locked parametric oscillator based on a nonlinear LBO crystal pumped by XeCl- and dye-laser systems is developed. The nonlinear refractive index n2 approximately equals 1.7 10-16 cm2/W and the optical surface breakdown threshold Ibr approximately equals 3.8 1013 W/cm2 of LBO crystal for approximately 400 fsec pulses were measured. The spatial dispersion of effective nonlinearity deff2/n3 for parametric amplification in LBO crystal is calculated. The design and performance of femtosecond dye- laser system and XeCl-excimer-laser system capable of producing a focused intensity in excess of 1016 W/cm2 are described.

Soft x-ray production and harmonic generation in femtosecond laser-driven plasma

The picosecond soh X-ray source based on femtosecond laser-driven plasma and spherical multilayred mirrors is developed. Results on VUV laser plasma spectrum. investigation and second harmonic generation are reported.

Ultrafast Lattice Dynamics in FeRh during a Laser-Induced Magnetic Phase Transition

Time-resolved X-ray diffraction is used to study the lattice response of FeRh during a laser-driven anti-ferromagnetic to ferromagnetic phase transition. The experiments reveal a fast and a slow component in the induced expansion dynamics.

Enhanced nonlinear optics with photonic-crystal and microstructure fibers

The mode structure of supercontinuum emission generated by 40-fs pulses of 800-nm Ti:sapphire laser radiation in fused silica microstructure fibers is experimentally studied. The long-wavelength and visible parts of supercontinuum emission are shown to be spatially separated in microstructure-fiber models. With an appropriate spectral filtering, bell-shaped modes of the long-wavelength section (~720-900 nm) of the supercontinuum generated in a microstructure fiber with a small core diameter can be separated from either doughnut-like or bipartite modes of the visible part (~400-600 nm) of this supercontinuum. This effect can be employed to spectrally slice single modes of supercontinuum emission from microstructure fibers.

Enhanced spectral broadening and spectral distortions of short laser pulses in holey fibers

The influence of the structure of the holey-fiber cladding on the spectral broadening of femtosecond laser pulses is experimentally studied. These experiments demonstrate that the spectral broadening of 70-fs pulses of 800 nm Ti:sapphire laser radiation transmitted through 2- and 3- micrometers -pitch holey fibers can be enhanced by a factor of about 1.5 by increasing the air-filling fraction of the fiber cladding from 16 up to 65%. The main physical factors influencing the phase distribution and coherence properties of broadly spanning frequency combs produced with the use of holey fibers are considered. Phase shifts and spectral distortions arising due to dispersion effects, modulation instabilities, and shock waves of pulse envelopes are explored, and general recipes to reduce the influence of these effects by means of fiber optics are discussed.

Holey fibers with 0.4-to 32- μ m-lattice-constant photonic band-gap cladding: fabrication, characterization, and applications

The results of experimental and theoretical studies of the properties of holey fibers are presented. The fabrication of holey fibers with a pitch of the two-dimensional periodic structure of the cladding less than 500 nm allowed us to experimentally observe a photonic band gap in transmission spectra of holey fibers tunable within the range of 930 - 1030 nm. It is demonstrated that holey fibers provide an opportunity to considerably increase the efficiency of spectral broadening and phase control of short laser pulses as compared with conventional fibers.

Excitation of Surface Electromagnetic Waves in High-Temperature Near-Surface Plasmas; Resonance Second Harmonic Generation

Surface electromagnetic waves are excited in plasma that is generated on a solid target surface by 200 fs laser pulses with the intensity of 1015 W/cm2. Increase in second harmonic efficiency for s- and p-polarized pump under resonant SEW excitation is obtained. Estimations on possible local field enhancement are made.

Interaction of superintense femtosecond laser pulses with freely suspended thin films

In this paper some advantages of using thin freely suspended films as a target in femtosecond laser-plasma interaction are discussed. It is shown by numerical simulation for carbon film, that for 10 - 30 nm films significant increase in plasma temperature can be achieved due to strongly limited thermoflux deep into the target. This increase in temperature is accompanied by increase in x-ray yield. The other task of this work is to investigate whether it is possible to excite surface plasmon-polariton for the thin film target.

Focusing of picosecond x-ray pulses on the target at power densities up to 1 GW cm-2

The x ray emission from femtosecond laser-driven plasma has been investigated using spherical multilayered mirrors. Different laser pulse widths have been used. The conditions required to produce high intensity x ray emission (up to 1011 W cm-2) from H-like excited ions are discussed.