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  • 1
    Digitale Medien
    Digitale Medien
    Growth of a spike on a laser beam in a plasma (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1221-1223 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An on-axis spike in the intensity distribution of a Gaussian laser beam grows rapidly as the beam propagates in a laser-produced plasma. The nonlinearity arises through the ponderomotive force and has a saturating behavior. For vosc ∼vth, the optimum spike radius is approximately a few c/ωp0 and the amplification length is ∼2cω/ω2p0, where ωp0 is the unperturbed plasma frequency, ω is the radiation frequency, and vosc and vth are oscillatory and thermal velocities of electrons, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859259
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  • 2
    Digitale Medien
    Digitale Medien
    Hot carrier diffusion induced instabilities of electromagnetic waves in plasmas and semiconductors (1973)
    Springer
    Optical and quantum electronics 5 (1973), S. 509-516 
    Details
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract The stability of a plasma/semiconductor for small fluctuations in the intensity of plane electromagnetic beam has been studied when a non-linearity in the dielectric constant appears on account of the diffusion of non-uniformly heated carriers (due to fluctuations in the intensity of the beam). Fluctuations of optimum size and long duration have been found to grow at moderate powers. The effect of absorption is, however, to suppress this effect.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02109656
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  • 3
    Digitale Medien
    Digitale Medien
    Self-focusing of a laser beam in a strongly ionized plasma (1973)
    Springer
    Optical and quantum electronics 5 (1973), S. 533-538 
    Details
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract In the presence of a strong Gaussian laser beam, the non-linearity in the dielectric constant of a strongly ionized plasma has been investigated. The non-linearity arises due to the heating and redistribution of the electrons; the loss of electron energy gained from the field has been assumed to be due to thermal conduction. This self-induced non-linearity causes a self-focusing and oscillatory waveguide propagation of the beam even when the non-linear dielectric constant does not fall in the saturating range. In a typical case of a 1010 W laser, the enhancement of axial intensity by a factor of 25 has been predicted in a length of 0.6 cm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02109658
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  • 4
    Digitale Medien
    Digitale Medien
    Self-focusing of electromagnetic waves in a magnetoplasma (1974)
    Springer
    Optical and quantum electronics 6 (1974), S. 167-180 
    Details
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract The steady state self-focusing of a Gaussian electromagnetic beam in a magneto-plasma has been studied. On a short time scale, a non-linearity in the dielectric constant of a plasma appears due to the ponderomotive force. This force in the case of the extraordinary mode has opposite signs forω〉ω c andω〈ω c, whereω c is the electron cyclotron frequency. The self-focusing due to this effect is predicted at frequencies except forω c /2〈ω〈ω c . The focusing of the ordinary mode is adversely affected by the magnetic field. On a larger time scale, the non-uniform heating of electrons by the beam and the resulting redistribution of the electron density is a source of non-linearity. This non-local non-linearity is several orders of magnitude higher than the ponderomotive non-linearity. We predict self-focusing of the extraordinary mode only above the gyroresonance (ω〉ω c ), while the ordinary mode can be focused at all frequencies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01419065
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  • 5
    Digitale Medien
    Digitale Medien
    Waveguide propagation of laser beams in media with saturating non-linearity (1971)
    Springer
    Optical and quantum electronics 3 (1971), S. 171-175 
    Details
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract The waveguide propagation of Gaussian laser beams in dielectric media with saturating non-linearity has been investigated analytically, using two profiles for the dependence of the dielectric constant on intensity. An expression for the radius of the uniform wave-guide, corresponding to a given power of the beam, has been obtained and the existence of a minimum radius, corresponding to an optimum power, has been predicted. For high power laser beams, oscillatory waveguides have been obtained; for very high powers the oscillations of the radius of the waveguide are small.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01419333
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  • 6
    Digitale Medien
    Digitale Medien
    Self-focusing of laser beams in inhomogeneous dielectrics (1971)
    Springer
    Optical and quantum electronics 3 (1971), S. 157-161 
    Details
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract This paper presents a theoretical investigation of the propagation and focusing of an electromagnetic wave in an inhomogeneous dielectric whose dielectric constant is given byɛ=ɛ 0(z)+Φ(r, z), whereZ-axis is the direction of propagation of the beam. The quantity Φ(r, z) may either be due to non-linear effects or due to inhomogeneity in the actual fabrication of the guide. Numerical calculations show that for a cylindrically symmetrical Gaussian beam, even a small axial inhomogeneity has appreciable effect on self-focusing; if the real part ofdɛ 0 (z)/dz is larger than zero the focusing effect increases withz, and vice-versa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01419331
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  • 7
    Digitale Medien
    Digitale Medien
    Mobility of electrons in nondegenerate semiconductors considering electron-electron scattering (1958)
    Springer
    The European physical journal 150 (1958), S. 242-246 
    Details
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Spitzer andHärm [1] have investigated the velocity distribution of electrons in the presence of a weak electric field in an ionized gas. Introducing the concept of time of relaxation τ′, due to electron-ion and electron-electron scattering, and using the results ofSpitzer andHärm [1], the authors have obtained an expression for τ′ which is applicable to semiconductors with little modification. In this paper the authors have used this expression for τ′ to obtain the mobility of electrons in nondegenerate semiconductors, taking into account the scattering by lattice vibrations, electron-ion interactions and electron-electron interactions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01325719
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  • 8
    Digitale Medien
    Digitale Medien
    Nonlinear thermal diffusion of electrons in ionized gases (1966)
    Springer
    The European physical journal 195 (1966), S. 13-19 
    Details
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The authors have obtained a solution of Boltzmann's transfer equation for electrons in a slightly ionized gas and a simple model semiconductor, in the presence of a high temperature gradient. An explicit expression for f0(the isotropic part of the electron velocity distribution function) correct to terms involving the square of the temperature gradient has been obtained. Using this solution, explicit expressions for non-linear electric and thermal current densities due to high temperature gradient have been obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01326375
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  • 9
    Digitale Medien
    Digitale Medien
    Steady state and transient self-interaction of a laser beam in a strongly ionized moving plasma (1975)
    Springer
    Applied physics 7 (1975), S. 187-193 
    Details
    ISSN: 1432-0630
    Schlagwort(e): Self-interaction of a laser beam ; Strongly ionized moving plasma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The steady state and transient self-interaction of a laser beam with a strongly ionized plasma flowing transverse to the direction of propagation have been investigated by a phenomenological approach using perturbation theory, WKB and paraxial ray approximations. The effect of the transverse motion of the plasma has been included by a convection term in the energy balance equation and is found to result in the non-symmetrical heating of electrons. As a result the beam is shifted towards the direction of transverse flow of the plasma by an amount that increases with the flow velocity. The extent of asymmetry in self-focusing along the transverse directions is, however very small. In a typical case of 7.6×105 watt laser of ω=104 GHz and initial beam widthr 0=0.05 cm the transverse shiftx p=0.1r 0 is predicted in a distance of propagationz=0.34 cm in a strongly ionized plasma of electron densityN e=1016 cm−3 and transverse flow velocityW 0=107 cm/sec.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00936023
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  • 10
    Digitale Medien
    Digitale Medien
    Modulation of electromagnetic waves by time-dependent magnetic fields in a ferrite (1975)
    Springer
    Applied physics 8 (1975), S. 23-27 
    Details
    ISSN: 1432-0630
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The modulation of phase and amplitude of an electromagnetic wave in a ferrite by a longitudinal, time-dependent (sinusoidally modulated) magnetic field has been investigated. In the case of an infinite medium, an analytical expression for the amplitude envelope of the wave is obtained and it is found that the envelope differs appreciably from the sinusoidal form. In the case of a ferrite slab, the amplitude of the transmitted and the reflected components of the magnetic vector have been evaluated by an expansion method. Numerical calculations indicate, as expected, that for a uniform plane wave incident on a ferrite sheet of finite thickness, the transmitted beam is strongly amplitude modulated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883665
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