Propagation and compression of pulses in media with dispersion losses
Propagation and compression of pulses in media with dispersion losses
Yu.E. D'yakov
The spectral and temporal behavior of pulses propagating in selectively absorbing and amplifying media has been described. Optimization of pulse shape, compensation for dispersional distortions, and some new methods of compression based on dispersion losses are discussed. The evolution of the Gaussian FM pulse in a "parabolic" medium showing a square complex dispersion characteristic has been considered in detail, in particular, in a laser SRS amplifier. General estimates have been obtained for the energy in the "wings" of the pulse or its frequency spectrum.
Show AbstractSpectral characteristics of thin-layer interference filters
Spectral characteristics of thin-layer interference filters
A.V. Kosar', A.V. Kozlov
A theoretical study has been carried out of the spectral characteristics (the wavelength dependence of radiant transmittance) of thin-layer interference filters (the total optical density of the structure is smaller than half a wavelength). Simple analytical expressions have been obtained that enable one to adequately determine the position and depths of all the extrema on the spectral characteristics of these interference filters. The specific features of the structures under consideration and the potentialities for their utilization in applied optics have been studied and discussed. The computer-aided numerical analysis confirmed the theoretical predictions.
Show AbstractResonance excitation of surface electromagnetic waves on diffraction gratings in the IR region: anomalies of absorption and reflection
Resonance excitation of surface electromagnetic waves on diffraction gratings in the IR region: anomalies of absorption and reflection
A.A. Karabutov, I.A. Kudinov, V.T. Platonenko, M.A. Sogoyan
Absorption of the IR radiation by metallic diffraction gratings was studied by using the optoacouatic effect. Narrow peaks that correspond to resonance excitation of surface electromagnetic waves (SEW) were discovered. The dependence of peak widths was investigated as a function of the SEW pathlength and the width of the angular spectrum of radiation. The macroscopic redistribution of radiation intensity was discovered experimentally in the beam specularly reflected from the grating.
Show AbstractThe use of laser saturation fluorometry for the study of mechanisms of chlorophyll a fluorescence build-up in phytoplankton under conditions of mineral nutrition shortage
The use of laser saturation fluorometry for the study of mechanisms of chlorophyll a fluorescence build-up in phytoplankton under conditions of mineral nutrition shortage
M.Yu. Gorbunov, V.V. Fadeev, A.M. Chekalyuk
The increase in the intensity of chlorophyll a fluorescence of phytoplankton under conditions of shortage of mineral nutrition was found to have two components. The first component, whose relative contribution to the overall process of fluorescence intensity change makes up 60-75%, is of a recombination origin and is due to a disruption of the electron transport between the intermediate acceptor Pheo and the primary quinone acceptor $Q_A$ in the reaction center of photosystem II (PS II). The second, nonrecombination, component is due either to weakening of the bond between the light-harvesting antenna and the PS II reaction center, or to disruption of the electron transport between the primary donor P680 and Pheo. It is shown that shortage of mineral nutrition results in the formation of certain number of nonreactive PS II reaction centers with disrupted electron transport from $Q_A$ to the secondary quinone acceptor $Q_B$.
Show AbstractProbability description of delayed fluorescence in higher plants for the model of the reaction center complex of photosystem II
Probability description of delayed fluorescence in higher plants for the model of the reaction center complex of photosystem II
A.K. Kukushkin, V.A. Ryabov, E.A. Soldatova
The probability method was used to describe delayed fluorescence of higher plants. The simplest model proposed is based on the notion of a complex of reaction centers in photosystem Il in which exposure to light induces separation of charges. The model includes pigments, donors and acceptors of electrons with a disrupted electron transport chain, with and without consideration for the nonradiative transition. The results obtained show that a multiexponential decay and a nonmonotonic kinetics of delayed fluorescence may arise in the course of back reactions occurring at the initial stages of electron transfer.
Show AbstractStimulated Raman backscattering of the Gaussian pumping pulse: numerical experiment
Stimulated Raman backscattering of the Gaussian pumping pulse: numerical experiment
S.Yu. Nikitin, D.A. Sivashov
In this paper we have studied the dynamics of stimulated Raman backscattering (SRBS) of the Gaussian pumping pulse in the plane wave approximation and without allowance for local nonstationarity. Three basic dynamic regimes have been revealed: quasistatic, modulation (spiking), and SRBS regime in an unbounded medium. The conditions for realization and the principal characteristics of these regimes have been established.
Show AbstractStaebler-Wronski effect in amorphous hydrogenated p-type silicon films
Staebler-Wronski effect in amorphous hydrogenated p-type silicon films
A.G. Kazanskii
Illumination-induced variations of dark conductivity in amorphous hydrogenated silicon films ($\alpha$-Si:Н) doped with boron at different concentrations were investigated. Measurements were carried out in the 270 to 470 K temperature range. Three processes leading to conductivity variation were revealed. Two of them cause an increase in conductivity and are related to the film surface. The third process occurs in the bulk. The possible mechanisms of these processes are considered.
Show AbstractA multichannel detector of low-frequency GW-bursts based on laser deformograph
A multichannel detector of low-frequency GW-bursts based on laser deformograph
A.V. Gusev, V.K. Kravchuk
The possibility of using a laser deformograph as a detector of low-frequency GW-bursts in active filtering of seismic interferences under conditions of incomplete a priori information is considered.
Show AbstractOn the contribution of the vector component of torsion to the effect of interaction of polarized photons
On the contribution of the vector component of torsion to the effect of interaction of polarized photons
I.V. Yakushin
It is shown that the purely vector part of torsion in the first-order perturbation theory with respect to the constant of interaction between the torsional and electromagnetic fields gives no contribution to the effect ·of interaction of polarized photons in the vapor of sodium atoms.
Show AbstractThe influence of thermal motion of electrons on a strongly nonlinear Langmuir wave
The influence of thermal motion of electrons on a strongly nonlinear Langmuir wave
I.M. Aleshin
The stationary nonlinear Langmuir wave is investigated by the method of kinetic equation. The Maxwellian distribution is employed as the initial velocity distribution of electrons. The asymptotic Laplace method is used to find the nonlinear current. In contrast to the "water bag" type distribution, the limitation on the wave field amplitude is removed.
Show Abstract