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Overmodulation of an upper hybrid electromagnetic beam in a plasma
Author(s) -
Sharma R. C.,
Sharma R. R.
Publication year - 1981
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs016i003p00409
Subject(s) - ponderomotive force , physics , m squared , laser beam quality , envelope (radar) , beam (structure) , amplitude , optics , laser , atomic physics , beam diameter , plasma , electron , beam parameter product , quantum mechanics , laser beams , telecommunications , radar , computer science
Using the fluid equations for the nonlinear response of electrons, we have studied the self distortion of an amplitude‐modulated upper hybrid laser beam and a Gaussian laser pulse in a collisionless magnetoplasma. The beam possesses a Gaussian distribution of intensity in the transverse plane and gives rise to a ponderomotive force on the electrons. The parallel component of ponderomotive force causes a redistribution of electron density, which gets modulated at the modulation frequency of the beam, the profile of modified electron density results in the selffocusing of the beam. The high‐ and low‐amplitude portions of the beam are focused to different extents, and a severe distortion in the amplitude envelope of the beam results. For a typical 10.6‐μ, CO 2 laser of 10 8 W the change in the index of modulation becomes ∼100% after propagating a distance ∼0.4 cm. Similarly, the intensity envelope of a Gaussian laser pulse also gets severely distorted as it propagates in the plasma.