Self focusing of a quadruple Gaussian laser beam in a plasma
- Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)
The self focusing of a quadruple Gaussian laser beam, comprising four coherent identical Gaussian beams with axes parallel to z-caret but shifted from z-axis by -x{sub 0}x-caret,x{sub 0}x-caret,-x{sub 0}y-caret,x{sub 0}y-caret in a collisionless plasma, is investigated in the paraxial ray approximation. The nonlinearity arises through the ponderomotive force led plasma density redistribution. As the beam propagates, it maintains the shape of its intensity profile with spot size r{sub 0} of each of the four distributions modified from r{sub 0} to r{sub 0}f, x{sub 0}, modified to x{sub 0}f and the axial intensity enhanced by 1/f{sup 2}, where f is the beam width parameter. In the regime of quadratic nonlinearity, the threshold beam power for self focusing, P{sub th}, increases with x{sub 0} as the laser intensity gradient decreases and the ponderomotive force becomes weaker. At beam power greater than P{sub th}, the beam focuses in an oscillatory manner, i.e., f varies periodically with z due to the saturating effect of nonlinearity. The locations of intensity maxima of the four beams also vary periodically with z. As x{sub 0} increases from 0 to 0.6r{sub 0}, the transverse intensity gradient becomes weaker and the rate of self focusing, i.e., the rate of variation of f with z decreases.
- OSTI ID:
- 22086122
- Journal Information:
- Physics of Plasmas, Vol. 19, Issue 9; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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