A V Bogatskaya

On the possibility of a short subterahertz pulse amplification in a plasma channel created in air by intense laser radiation

The evolution of the electron energy distribution function in the plasma channel created in air by a UV-laser pulse of femtosecond duration is studied. It is shown that such a channel can be used to amplify few-cycle electromagnetic pulses in the subterahertz frequency range at the time of relaxation of the energy spectrum in air determined by the vibrational excitation of the nitrogen molecules. The gain factor as a function of time, electron concentration and frequency of the amplifying radiation is obtained. The propagation of few-cycle radio-frequency pulses through the amplifying medium is analysed.

Polarization response in extreme nonlinear optics: when can the semiclassical approach be used?

Availability of the semiclassical approach in strong-field physics and extreme nonlinear optics is analyzed. It is found that it is valid for calculation of the emission to the initially populated bound state only if population of this state is close to unity during the pulse and in the after pulse regime. If the initial level is depleted, the semiclassical approach fails and should be replaced by quantum-electrodynamical calculations. Also it is demonstrated that the bremsstrahlung spectrum cannot be correctly described in the frames of the semiclassical approach.

Guiding and amplification of microwave radiation in a plasma channel created in gas by intense ultraviolet laser pulse

The evolution of non-equilibrium plasma channel created in xenon by powerful KrF-femtosecond laser pulse is studied. It is demonstrated that such a plasma channel can be used as a waveguide for both transportation and amplification of the microwave radiation. The specific features of such a plasma waveguide are studied on the basis of the self-consistent solution of the kinetic Boltzmann equation for the electron energy distribution function in different spatial points of the gas media and the wave equation in slow-varying amplitude approximation for the microwave radiation guided and amplified in the channel.

Interference stabilization and UV lasing in a plasma channel formed in gas by intense RF field

The effect of interference stabilization of Rydberg atoms in a high-intensity IR laser field is proposed to create a plasma channel with population inversion for conversion of the input laser energy into the VUV and XUV frequency band.

Prospects of odd and even harmonic generation by an atom in a high-intensity laser field

New approach to study the spontaneous emission of the atomic system in the presence of the high-intensity laser field is used to study the process of harmonic generation. The analysis is based on the consideration of quantum system interaction with quantized field modes beeing in vacuum state, while the intense laser field is considered classically beyond the perturbation theory. The numerical analysis of the emission from the single one-electron one dimensional atom irradiated by the femtosecond laser pulse of Ti-Sa laser is discussed. It is demonstrated that not only odd but also even harmonics can be emitted if the laser field is strong enough. The origin of appearance of even harmonics is studied. The obtained results are compared with that found in the frames of semiclassical approach widely used to study the harmonic generation. It is found that semiclassical approach is inapplicable in the strong-field limit.

Spontaneous emission of atoms in a strong laser field

The spontaneous emission of an atomic system in the field of a high-intensity femtosecond laser pulse is considered within the framework of a consistent quantum-mechanical approach based on an examination of the interaction of a quantum system with a set of quantized field modes in a vacuum state. Both even and odd harmonics of the driving field are shown to appear in the atomic emission spectrum, and the mechanisms of their generation are elucidated. A comparison with the semiclassical theory of laser harmonic generation is made. The semiclassical approach in describing the spontaneous emission in strong laser fields, especially under conditions of significant depletion of the ground (initial) state in a laser field, is shown to be limited.

Amplification and lasing in a plasma channel formed in gases by an intense femtosecond laser pulse in the regime of interference stabilization

The effect of the interference stabilization of Rydberg atoms in a high-intensity laser field is proposed to create a plasma channel with population inversion between a set of Rydberg states and the low-lying excited and ground state for the conversion of the input laser energy into the visible or VUV and XUV frequency band. Furthermore, there is a possibility of creating population inversion between high-lying Rydberg states that can be used for lasing and amplification in the IR, mid-IR, and terahertz frequency band.

Nonequilibrium plasma channel in gaseous media formed by powerful UV laser as a waveguide for transportation and amplification of short microwave pulses

The evolution of strongly nonequilibrium plasma in a channel created in gaseous media by powerful UV femtosecond laser pulse is studied. It is demonstrated that such a plasma channel can be used as a waveguide for both transportation and amplification of the microwave radiation. The specific features of such a plasma waveguide are studied on the basis of the self-consistent solution of the kinetic Boltzmann equation for the electron energy distribution function in different spatial points of the gas media and the wave equation in paraxial approximation for the microwave radiation guided and amplified in the channel. The results of modeling for rare gases (xenon) and air are compared. The amplification factor in xenon plasma in dependence on channel radius, intensity and frequency of the input RF radiation is analyzed.

Propagation of a Short Subterahertz Pulse in a Plasma Channel in Air Created by Intense UV Femtosecond Laser Pulse

The evolution of the electron energy distribution function in the plasma channel created in air by the third harmonic of the Ti:Sa-laser pulse of femtosecond duration is studied. It is shown that strong nonequilibrium of such a plasma leads to the possibility to use the channel for guiding and amplification of few-cycle electromagnetic pulses in subterahertz frequency range at the time of relaxation of the energy spectrum in air determined by the vibrational excitation of the nitrogen molecules. The refractive index and the gain factor as a function of time, electron concentration and frequency of the amplifying radiation are obtained. The propagation of few-cycle radio-frequency pulses through the amplifying medium is analyzed.

Interference stabilization and possibility of amplification and lasing in plasma channel formed in gas by intense femtosecond laser field

The effect of interference stabilization of Rydberg atoms in high-intensity laser field is proposed to create the plasma channel with population inversion between set of Rydberg states and the ground state for conversion of the input laser energy into the VUV and XUV frequency band. Furthermore, there is a possibility to create a population inversion between high-lying Rydberg states which can be used for lasing and amplification in the IR, mid-IR and sub-terahertz frequency band.