P. A. Chizhov

Superluminal source of directional pulsed wideband electromagnetic radiation

A photoemission source of directional pulsed wideband electromagnetic radiation in the microwave region is developed, and the time profile of the generated pulse is investigated. The source is a vacuum photodiode of a parabolic shape in which a Cherenkov radiation pulse is formed by an electron current wave excited by an incident laser pulse and propagating along the surface of the anode mesh with a phase velocity higher than the speed of light.

Optimal polarization of a two-colored pump for terahertz generation with a phase-unstable scheme

The polarization properties of a scheme for terahertz (THz) generation by an optical breakdown of a gaseous media using a two-colored femtosecond pulse are investigated. It is found that if the scheme is not stabilized over the phase shift between the pump waves, the maximal THz signal is observed when the pump pulses are elliptically polarized. At this rate the stability of the THz signal power is also maximal. These observations are in compliance with a photocurrent model of THz generation.

Backward Terahertz Radiation from a Two-Color Femtosecond Laser Filament

We report the first experimental observation of backward terahertz emission from the two-color laser induced plasma filament in air. The ratio of measured forward-to-backward terahertz radiation is ∼25/1. This result agrees with numerical simulations based on interferometric model assuming 0.3 mm long plasma source.

Interferometry diagnostics of plasma channel of femtosecond filament

Results of the electron density dynamics in the plasma channel of a femtosecond filament in air, nitrogen and argon from the moment of ionization up to hundreds of picoseconds after it are presented. Anisotropy of the refractive index was found, which is preceded and accompanied by ionization of the gas at the time of passage of high-intensity femtosecond laser pulse.

The dependence of terahertz signal and third harmonic amplitudes on mutual polarization of two-color pump components under optical breakdown of air

In this paper we measured the dependence of the signal of the third harmonic and terahertz radiation on the mutual polarization of the first and second harmonic to compare the mechanisms of their generation. For this purpose we used the output radiation of laser system Spitfire pro with the following parameters: pulse duration 35 fs, central wavelength 800nm, repetition rate 1kHz, energy of the first and second harmonic are 2mJ and 240mJ respectively. The radiation was focused by parabolic mirror with focal length 7,5 cm in air. The energy of terahertz and third harmonic radiation was measured by Holey cell and photomultiplier respectively.

Optimization of the laser plasma source of terahertz radiation and interferometric study of its spatio-temporal field distribution

The efficiency of terahertz radiation generation induced by focusing two-color femtosecond laser pulses in the air with different polarization state of the pump fields was studied. A new measurement technique for the detection of the spatio-temporal THz electric field strength distribution in an electro-optic crystal using optical interferometry was demonstrated.

Features of the electron density dynamics in the filamentation of femtosecond laser radiation in air at elevated pressure

The electron density in the plasma channel of a femtosecond filament in air at pressures from 1 to 7 atm is measured at different instants, starting from the ionisation onset and up to several hundreds of picoseconds after it. The initial electron density is found to increase sharply in the pressure range of 3 – 4 atm. The plasma channel diameter is found to decrease with an increase in pressure from 3 to 7 atm.

Picosecond Laser System 193 nm Based On Solid State Nd:YAG Laser, Parametric Oscillator And ArF Amplifier.

Realized method of producing high-power picosecond UV pulses at a wavelength of 193 nm. Nd: YAG laser is used, followed by radiation and nonlinear transformations in the excimer gain medium to an energy of 10 mJ, a wavelength of 193 nm.

Femtosecond filament plasma channel formation and decay study by transverse optical interferometry

Electron density dynamics in gases is studied from ionization to hundreds of picoseconds after it by interferometry method. Optical refractive index anisotropy, which precedes and accompanies ionization, related with intense pulse propagation is revealed.

Generation of terahertz radiation due to air breakdown induced by two-frequency laser pulses with different polarization states

Generation of terahertz radiation during the focusing of dual-frequency femtosecond laser pulses with different polarization states in air is investigated. The dependence of the average power on the degree of ellipticity of the fundamental harmonic is obtained. Calculations based on the nonstationary photocurrent model are performed.