Plasmas and Various Nonlinearities, Causing Self Focusing Effect

Abstract

Non linear effecs have been found to be the overpowering  in laser produced plasmas, rf heating of plasmas, laser induced dielectric breakdown, laser-semiconductor interaction, optical fiber communication and several other areas. In plasmas, they arise when the refractive index is an increasing function of intensity due to relativistic mass nonlinearity, ponderomotive nonlinearity or Ohmic heating non-linearity. A Gaussian electromagnetic beam, thus creates a self induced refractive index profile. The axial portion of the wavefront travels with slower phase velocity whereas the marginal rays travel faster and give rise to curvature in the wave front, causing convergence of the beam. When nonlinear convergence supercedes diffraction divergence, the beam self focuses.