A. O. Levchenko

Transfer of microwave radiation in sliding mode plasma waveguides

A new regime of the sliding propagation of microwave radiation in plasma waveguides in atmospheric air has been investigated experimentally and theoretically. A plasma waveguide whose radius is much larger than the radiation wavelength has been created by the photoionization of an easily ionized impurity by the ultraviolet radiation of a KrF laser. The transfer of a 35.3-GHz microwave signal to a distance of 60 m has been demonstrated. The transfer mechanism is due to the total internal reflection of the wave on the optically less dense walls of the plasma waveguide.

Microwave energy channeling in plasma waveguides created by a high-power UV laser in the atmosphere

The grazing mode of microwave propagation in a hollow plasma waveguide formed by ionization of atmospheric air with a small easily ionized additive by strong UV pulses of the Garpun KrF laser (λ = 248 nm, the pulse duration and energy are ∼70 ns and ∼50 J) was experimentally demonstrated for the first time. The annular laser beam produced a hollow tube ∼10 cm in diameter with an electron density of ∼1012 cm−3 in a plasma wall ∼1 cm thick, over whichmicrowave radiation with λmw ∼ 8 mm was transmitted to a distance of 60 m. Themicrowave signal transmitted by the waveguide was amplified by a factor of 6 in comparison with propagation in free space.

Hydrodynamic instability and self-organization of a submicron relief on metal surfaces upon femtosecond laser exposure in liquids

Multishot exposure of nickel and iron surfaces by loosely focused femtosecond laser pulses in isopropyl alcohol resulted in quasi-regular arrays of submicron spikes and other intermediate self-organized structures. Such self-organized surface relief is considered to be formed via hydrodynamic instability of molten metallic surfaces in their contact with a near-critical alcohol vapor layer with the pressure of about 5 MPa.

Spectral dependence of the (2+1) resonance-enhanced multiphoton ionization (REMPI) of atmospheric oxygen around 248 nm laser wavelength

The spectral dependence of resonance-enhanced multiphoton ionization (REMPI) of oxygen in the atmospheric air was studied around the 248 nm laser wavelength. It is shown that (2+1) REMPI through the 3π_u intermediate Rydberg state took place. Rotational constant B of the 3π_u state was measured.

Electron-free UV laser pulse filamentation under coherent rotational SRS in air

Coherent stimulated rotational Raman self-scattering is proposed as the mechanism of electron-free filamentation of the ultra-short KrF laser pulse in air.

Amplification and generation of radiation at the 4{sup 2{Gamma}} {yields} 1,2{sup 2{Gamma}} transition of the Kr{sub 2}F molecule in an electron-beam-pumped wide-aperture laser

The radiation amplification and oscillation are obtained in an electron-beam-pumped Berdysh laser with an active volume of 10 L in the visible range from 430 to 470 nm at the broadband 42Γ → 1,22Γ transition in the triatomic Kr2F molecule of interest for amplification of ultrashort laser pulses. It is shown that, along with absorption of laser radiation in the active medium, the amplification dynamics is considerably determined by short-lived absorption induced in the amplifier windows by bremsstrahlung X-rays. For the specific pump power 0.6 — 0.7 MW cm-3, the gain, corrected for nonstationary absorption, was ~10-3 cm-1. A scheme of a Kr2F amplifier is proposed for amplification of ultrashort pulses up to multiterawatt peak powers in the active volume ~10 L.

Laser implantation of sodium nitrite into artificial opal pores upon exposure of artificial opal samples to pulsed radiation of the ultraviolet laser

We present experimental results on the introduction (laser implantation) of ferroelectric NaNO2 into artificial opal pores upon exposure of a thin powder layer of sodium nitrite applied on the artificial opal surface to radiation of the ultraviolet excimer laser. Reflection spectra of broadband radiation from the laser-implanted sample surface are compared with the reflection spectra of pure initial opals, artificial opals impregnated with a saturated aqueous solution of sodium nitrite and evaporated from solvent, and samples in which NaNO2 was directly introduced in the form of a melt.