共查询到20条相似文献,搜索用时 31 毫秒
1.
A. A. Frolov 《Plasma Physics Reports》2018,44(1):40-54
The feasibility of dipole radiation of terahertz waves under the action of a femtosecond laser pulse on a cluster is demonstrated theoretically. It is shown that the dipole mechanism of terahertz radiation generation plays a decisive role in the interaction of a laser pulse with small-size clusters with a sufficiently high electron collision frequency. The dependences of the spectral, angular, energetic, and spatiotemporal characteristics of the terahertz signal on the density of free electrons in the cluster plasma under the conditions in which dipole radiation is dominant are investigated. It is shown that the energy of terahertz radiation is maximal under the resonance conditions, when the laser frequency coincides with the eigenfrequency of a spherical cluster. 相似文献
2.
A. A. Frolov 《Plasma Physics Reports》2010,36(4):318-335
The generation of terahertz electromagnetic radiation when a laser pulse propagates through a low-density plasma slab is considered.
It is shown that terahertz waves are excited because of the growth of a weakly damped, antisymmetric leaking mode of the plasma
slab. The spectral, angular, and energy parameters of the terahertz radiation are investigated, as well as the spatiotemporal
structure of the emitted waves. It is demonstrated that terahertz electromagnetic wave fields are generated most efficiently
when the pulse length is comparable to the slab thickness. 相似文献
3.
A. A. Frolov 《Plasma Physics Reports》2007,33(12):1014-1022
The generation of low-frequency (terahertz) electromagnetic radiation in the reflection of a laser pulse from the boundary of a dense plasma is considered. Low-frequency wave electromagnetic fields in vacuum are excited by a vortex electric current that is induced at the plasma boundary by the ponderomotive force of the laser pulse. The spectral, angular, and energy parameters of the low-frequency radiation, as well as the spatiotemporal structure of the emitted waves, are investigated. It is shown that for typical parameters of present-day laser plasma experiments, the power of terahertz radiation can amount to tens of megawatts. 相似文献
4.
A theory is presented of the generation of low-frequency transition radiation by a short laser pulse at a plasma-vacuum interface. The wave electromagnetic fields are excited by the vortex electric current that is generated at the plasma boundary by the ponderomotive force of the laser field. The spectral, angular, and energy parameters of the transition radiation, as well as the spatiotemporal structure of the emitted waves in vacuum and in plasma, are investigated. It is shown that the parameters of the transition radiation depend essentially on the ratio of the laser pulse duration to the plasma oscillation period. Under conditions typical of present-day laser-plasma experiments, the transition electromagnetic radiation is generated in the terahertz frequency range and its power can reach several megawatts. 相似文献
5.
A. A. Frolov 《Plasma Physics Reports》2018,44(3):312-325
Generation of terahertz waves by hot dense plasma under the action of a femtosecond laser pulse in the regime of anomalous skin effect is considered. The spectral, angular, and energy characteristics of terahertz waves are studied as functions of the plasma and laser parameters. It is shown that, under the conditions of anomalous skin effect, which takes place in ultradense hot plasma, the total energy of the terahertz signal is independent of the electron density, proportional to the square of the electron temperature, and maximal at tight focusing of the laser pulse. 相似文献
6.
A. A. Frolov 《Plasma Physics Reports》2016,42(12):1111-1126
A theory of generation of terahertz radiation under laser–cluster interaction, developed earlier for an overdense cluster plasma [A. A. Frolov, Plasma Phys. Rep. 42. 637 (2016)], is generalized for the case of arbitrary electron density. The spectral composition of radiation is shown to substantially depend on the density of free electrons in the cluster. For an underdense cluster plasma, there is a sharp peak in the terahertz spectrum at the frequency of the quadrupole mode of a plasma sphere. As the electron density increases to supercritical values, this spectral line vanishes and a broad maximum at the frequency comparable with the reciprocal of the laser pulse duration appears in the spectrum. The dependence of the total energy of terahertz radiation on the density of free electrons is analyzed. The radiation yield is shown to increase significantly under resonance conditions, when the laser frequency is close to the eigenfrequency of the dipole or quadrupole mode of a plasma sphere. 相似文献
7.
A. A. Frolov 《Plasma Physics Reports》2013,39(2):155-166
A theory is developed enabling one to calculate the temporal profile and spectrum of a terahertz wave packet from the energy of the second harmonic of optical radiation generated during the nonlinear interaction between terahertz and circularly polarized laser pulses in the skin layer of an overdense plasma. It is shown that the spectral and temporal characteristics of the envelope of the second harmonic of optical radiation coincide with those of the terahertz pulse only at small durations of the detecting laser radiation. For long laser pulses, the temporal profile and spectrum of the second harmonic are mainly determined by the characteristics of optical radiation at the carrier frequency. 相似文献
8.
Cherenkov emission from a short laser pulse propagating in an underdense plasma along a constant magnetic field is considered. The spectral, angular, energy, and spatiotemporal parameters of the emitted radiation are investigated. It is shown that the spectral content of the radiation and its directionality depend sensitively on the plasma and laser-pulse parameters. For instance, the most intense backward radiation at the upper hybrid frequency is generated by a tightly focused laser pulse. 相似文献
9.
Boev S. F. Vagin A. I. Solomatin S. Yu. Savostyanov D. V. Siluyanov V. V. Shmakov A. S. Zaitsev B. D. Teplykh A. A. Borodina I. A. Karavaeva O. A. Guliy O. I. 《Biophysics》2019,64(3):416-423
Biophysics - Abstract—The effect of pulsed terahertz radiation at a wavelength of 66 μm, a pulse duration of 100 ns, and a pulse energy of 200 mJ on a suspension of microbial cells was... 相似文献
10.
A. V. Bogatskaya E. A. Volkova A. M. Popov I. V. Smetanin 《Plasma Physics Reports》2016,42(2):113-134
The time evolution of a nonequilibrium plasma channel created in a noble gas by a high-power femtosecond KrF laser pulse is investigated. It is shown that such a channel possesses specific electrodynamic properties and can be used as a waveguide for efficient transportation and amplification of microwave pulses. The propagation of microwave radiation in a plasma waveguide is analyzed by self-consistently solving (i) the Boltzmann kinetic equation for the electron energy distribution function at different spatial points and (ii) the wave equation in the parabolic approximation for a microwave pulse transported along the plasma channel. 相似文献
11.
A. A. Frolov 《Plasma Physics Reports》2007,33(3):179-188
The excitation of surface waves by a laser pulse as it crosses a vacuum-plasma interface is considered. Surface waves are excited by a vortex electric current that is generated at the plasma boundary by the ponderomotive force of the pulse. The question is considered of how the duration and transverse dimensions of the pulse affect the spatiotemporal distribution and the spectral and energy parameters of the excited surface waves. 相似文献
12.
Skobelev I. Yu. Faenov A. Ya. Gasilov S. V. Pikuz T. A. Pikuz S. A. Magunov A. I. Boldarev A. S. Gasilov V. A. 《Plasma Physics Reports》2010,36(13):1261-1268
X-ray diagnostics of the interaction of femtosecond laser pulses with intensities of 1016–1018 W/cm2 with CO2 clusters and frozen nanosize water particles is carried out. The stage of cluster expansion and the formation of a plasma
channel, which governs the parameters of the formed X-ray radiation source and accelerated ion flows, is studied. The measurements
are based on recording spatially resolved X-ray spectra of H- and He-like oxygen ions. Utilization of Rydberg transitions
for spectra diagnostics makes it possible to determine plasma parameters on a time scale of t ∼ 10 ps after the beginning of a femtosecond pulse. The role of the rear edge of the laser pulse in sustaining the plasma
temperature at a level of ∼100 eV in the stage of a nonadiabatic cluster expansion is shown. The analysis of the profiles
and relative intensities of spectral lines allows one to determine the temperature and density of plasma electrons and distinguish
the populations of “thermal” ions and ions that are accelerated up to energies of a few tens of kiloelectronvolts. It is shown
that the use of solid clusters made of frozen nanoscale water droplets as targets leads to a substantial increase in the number
of fast He-like ions. In this case, however, the efficiency of acceleration of H-like ions does not increase, because the
time of their ionization in plasma exceeds the time of cluster expansion. 相似文献
13.
A. S. Kishinets Yu. V. Korobkin I. V. Romanov A. A. Rupasov A. S. Shikanov A. Moorti P. A. Naik P. D. Gupta 《Plasma Physics Reports》2004,30(3):235-240
Results are presented from experimental studies of discharge instabilities and the energy and temporal characteristics of a vacuum-diode X-ray source with a laser plasma cathode over a wide range of energies, intensities, and durations of the plasma-forming laser pulse. It is experimentally shown that the vacuum-discharge dynamics and radiation processes in different discharge stages substantially depend on the parameters of the laser radiation. The shortest recorded pulse duration (10 ns) of Ti K-line radiation (4.5 keV) with a total photon number of 1011 is achieved when the laser plasma cathode is produced by a laser pulse with a duration of 27 ps and an intensity of 1013 W/cm2. It is found that the contrast of characteristic emission against the bremsstrahlung background is maximum when discharge instabilities are suppressed and the accelerating voltage is three to four times higher than the threshold voltage for line excitation. 相似文献
14.
This review considers experimental research of the biological effects of terahertz radiation and their results, which provide a basis for medical application of laser terahertz radiation. Therapeutic and diagnostic uses of laser terahertz radiation are described with reference to preliminary basic investigations at the organismic, cell, and molecular levels. It is emphasized that preliminary basic studies of this kind are of importance as another avenue of research to design diagnostic and therapeutic techniques in addition to terahertz imaging and spectroscopy.
相似文献15.
The effect of two-step exposure of bacterial objects to infrared laser and microwave pulse radiations was studied. The effect is determined by the time interval between two excitation steps and pulse duration. It was shown that the biologically active dose of microwave radiation is much lower than that of infrared laser radiation; however, laser radiation induces a stronger cellular response. It was found that microwaves enhance the efficiency of infrared laser radiation. 相似文献
16.
Inverse bremsstrahlung heating and thermal electron-impact ionization of a metal cluster are analyzed with account for the spatial structure of the electromagnetic field. It is shown that, for a femtosecond IR radiation pulse with an intensity of ~1018 W/cm2 and for an iron cluster with an optimum radius of ~25 nm, the electron temperature is higher than 1 keV. In this case, the L shell of the ions is highly stripped. The X-ray bremsstrahlung yield from clusters with a radius greater than the skin depth is estimated. 相似文献
17.
Introduction of biomolecules into cells in living animals is one of the most important techniques in molecular and developmental biology research, and has potentially broad biomedical implications. Here we report that biomolecules can be introduced into single cells in living vertebrate embryos by photoporation using a femtosecond laser amplifier with a high pulse energy and a low repetition rate. First, we confirmed the efficiency of this photoporation technique by introducing dextran, morpholino oligonucleotides, or DNA plasmids into targeted single cells of zebrafish, chick, shark, and mouse embryos. Second, we demonstrated that femtosecond laser irradiation efficiently delivered DNA plasmids into single neurons of chick embryos. Finally, we successfully manipulated the fate of single neurons in zebrafish embryos by delivering mRNA. Our observations suggest that photoporation using a femtosecond laser with a high pulse energy and low repetition rate offers a novel way to manipulate the function(s) of individual cells in a wide range of vertebrate embryos by introduction of selected biomolecules. 相似文献
18.
K. A. Ivanov D. S. Uryupina N. Morshedian R. V. Volkov A. B. Savel’ev 《Plasma Physics Reports》2010,36(2):99-104
Results are presented from experimental studies of ion acceleration under the action of femtosecond laser pulses with an intensity
of 1017 W/cm2, incident onto the free surfaces of melted gallium and indium. The effect of the polarization direction of a linearly polarized
laser pulse and the amplitude of a short prepulse, which precedes the main pulse by several nanoseconds, on the parameters
of accelerated ions is investigated. It is found that, even for such a moderate laser intensity, the characteristic velocity
of fast ions ejected along the reflected beam is a factor of 1.5 higher than that of ions ejected along the normal to the
target surface. It is shown that, as the prepulse energy increases, the hard X-ray yield and the mean energy of hot electrons
increase substantially, whereas the velocity of both fast and slow ions decreases appreciably regard-less of laser polarization. 相似文献
19.
The problem of nonlinear Thomson scattering of a relativistically strong linearly polarized ultrashort laser pulse tightly focused into a spot with a diameter of D F ? λ (where λ is the laser wavelength) is solved. The energy, spectral, and angular distributions of radiation generated due to Thomson scattering from test electrons located in the focal region are found. The characteristics of scattered radiation are studied as functions of the tightness of laser focusing and the initial position of test particles relative to the center of the focal region for a given laser pulse energy. It is demonstrated that the ultratight focusing is not optimal for obtaining the brightest and hardest source of secondary electromagnetic radiation. The hardest and shortest radiation pulse is generated when the beam waist diameter is ?10λ. 相似文献
20.
A. A. Frolov 《Plasma Physics Reports》2003,29(6):503-511
A study is made of the interaction (“collision”) of two laser pulses with the same frequency but different durations, propagating toward one another in a low-density plasma. It is found that, in the interaction region, the excitation of small-scale plasma fields localized within a distance on the order of the length of the longer pulse is accompanied by the backscattering of each of the pulses. The frequency shift of the backscattered radiation and its duration depend strongly on the lengths of the interacting pulses. It is shown that the spectrum of the long backscattered radiation “tail” that arises behind the shorter pulse as a result of its interaction with the longer pulse contains satellites shifted from the laser frequency by the plasma frequency. 相似文献