Accession Number : ADA311493

Title :   Self-Guiding and Stability of Optical Beams in Gases Undergoing Ionization.

Descriptive Note : Interim rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC BEAM PHYSICS BRANCH

Personal Author(s) : Sprangle, P. ; Esarey, E. ; Krall, J.

PDF Url : ADA311493

Report Date : 31 JUL 1996

Pagination or Media Count : 102

Abstract : The propagation of intense optical beams in gases undergoing ionization is analyzed. Two types of optical beam modes are considered, a fundamental Gaussian and a higher-order radially-polarized beam. The propagation dynamics include the effects of diffraction, nonlinear self-focusing, and ionization. For sufficiently intense optical beams the neutral gas undergoes ionization, generating a plasma which tends to defocus the beam. An envelope equation governing the spot size for both types of beams is derived, analyzed, and solved numerically. Self-guided solutions, which result from a balancing of diffraction, plasma defocusing and nonlinear self-focusing, are analyzed for both types of beams. These equilibrium solutions are found to be unstable due to an ionization-modulation instability for which asymptotic growth rates are obtained. A self-guided inverse Cherenkov accelerator based on the highest-order radially-polarized mode is proposed and analyzed. In addition, the depletion of the optical field due to collision and ionization losses is analyzed and the attenuation length derived.

Descriptors :   *OPTICAL EQUIPMENT, *GASES, *IONIZATION, *BEAMS(RADIATION), PROPAGATION, OPTICAL PROPERTIES, OPTICS, POLARIZATION, STABILITY, SIZES(DIMENSIONS), DYNAMICS, NEUTRAL, PLASMAS(PHYSICS), INTENSITY, EQUILIBRIUM(GENERAL), NONLINEAR SYSTEMS, SOLUTIONS(GENERAL), DIFFRACTION, ATTENUATION, FOCUSING, LOSSES, MODULATION, RADIAL FLOW.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Optics
      Plasma Physics and Magnetohydrodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE