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A V Maslov

Publications and source records attributed to A V Maslov.

18 recordsLinked to original sources
PubMed2005

Quantum coherence in an optical modulator.

Semiconductor quantum well electroabsorption modulators are widely used to modulate near-infrared (NIR) radiation at frequencies below 0.1 terahertz (THz). Here, the NIR absorption of undoped quantum wells was modulated by strong electric fields with frequencies between 1.5 and 3.9 THz. The THz field coupled two excited states (excitons) of the quantum wells, as manifested by a new THz frequency- and power-dependent NIR absorption line. Nonperturbative theory and experiment indicate that the THz field generated a coherent quantum superposition of an absorbing and a nonabsorbing exciton. This quantum coherence may yield new applications for quantum well modulators in optical communications.

Journal Article↗
PubMed2004

Two-dimensional theory of Cherenkov radiation from short laser pulses in a magnetized plasma.

The Cherenkov wakes excited by intense laser drivers in a perpendicularly magnetized plasma are a potential source of high-power terahertz radiation. We present a two-dimensional (2D) theory of the emission of magnetized wakes excited by a short laser pulse. The 2D model reveals the important role of the transverse size of the laser pulse missed in previous simple one-dimensional estimations of the radiation. We derived expressions for the radiated fields and for the angular/frequency distribution of the radiated energy. Beats in the radiation pattern behind the moving pulse are predicted and explained. For the interpretation of existing experimental results, the time dependence of the energy flux parallel and perpendicular to the laser path is examined.

Journal Article↗
PubMed2004

Far-field emission of a semiconductor nanowire laser.

The polarization properties and angular distribution of intensity of the far fields from a nanowire laser are investigated. The far-field emission depends strongly on the mode type (HE11, TE01, TM01) and the radius of the nanowire. The emission is weakly directional, and a large part of it can be emitted in the backward direction. Our results can be applied for experimental determination of a lasing mode by its far fields as well as for optimization of laser emission.

Journal Article↗
PubMed2002

Interaction of an electromagnetic wave with a suddenly stopped ionization front.

The theory of the interaction of an electromagnetic wave with a uniformly moving ionization front in a gas is extended to include the case when the front suddenly stops. This nonstationary character of the wave/front interaction, which is typical for experiments carried out in a finite-size gas tube, gives rise to fresh physical effects. First, currents induced near the plasma boundary after the front stops produce a static magnetic field not only in the plasma behind the front but also in the vacuum ahead of the front. Second, in the regime where the transmitted wave falls off behind the front, the skinning field leaks through the stopped front and produces a burst of highly frequency up-shifted radiation.

Journal Article↗
PubMed2001

Interaction of an electromagnetic wave packet with an ionization front: copropagating configuration.

The interaction of a TM polarized wave packet with a moving ionization front is theoretically investigated. We extend our previous study [IEEE Trans. Plasma Sci. 27, 655 (1999)], where we considered the case when the wave packet is incident on the front, by including the case often used in experiments when the front overtakes the wave packet. We focus on the energy transformation into the generated waves-the point that is rarely addressed in literature due to complications arising from the presence of Langmuir waves. Our quantitative results show the importance of losses via Langmuir wave excitation compared to other possible losses due to the excitation of stationary transverse electron currents in the plasma. Applicability to the generation of frequency upshifted radiation is discussed.

Journal Article↗
PubMedDate not supplied

The functional role of the motor area of the cortex in the formation of riddance reactions in dogs.

A model of instrumental conditioning similar to the classical model (Pavlovian) is proposed. Flexion of the ipsilateral forelimb was elicited while EDS was applied to the hind limb by stimulation of the motor area of the cortex (M1); both stimuli ceased during the raising of the forelimb. Uniform combinations of this kind led to the development of forepaw flexion reactions in response to the EDS of the hind paw. Prolongation of EDS by 3 sec following cortical stimulation led to rapid extinction of the developed reactions. Thus, the possibility of the effective instrumentalization of movements induced by stimulation of the M1 is proven. This argues that the forming "instrumental" connection (drive-motor structures) is addressed directly to the M1.

Animals↗
PubMedDate not supplied

[The functional role of the motor area of the cortex in the acquisition of escape reactions in dogs].

The model of escape conditioning similar to classical (pavlovian) was proposed. During shock application to the hind limb (a conditioned stimulus) the ipsilateral foreleg flexion was elicited by a stimulation of the motor cortex (an unconditioned stimulus); both stimuli were turned off in the course of the forepaw lifting. Such uniform pairings resulted in elaboration of a reaction of the foreleg flexion in response to the shock. Prolonging the shock by 3 s after the cortical stimulation led to a rapid extinction of the acquired response. So a possibility to instrumentalize movements elicited by stimulation of the motor cortex (MI) was proved. This is in argument in favour of an assumption that the established "instrumental" connection (drive-motor structures) can be addressed directly to the motor cortex.

Animals↗