Structure of laserinduced normal modes in finite inhomogeneous plasma
Abstract
An analytic treatment of the problem of normal modes resulting from the decay of an electromagnetic pump wave propagating in a strongly inhomogeneous finite plasma is presented. Asymptotic solutions of the Weber equation and, alternatively, the WKB method, are applied to formulate dispersion relations which agree. Simple formulae for the complex growth rate p_{m} = ρ_{m}±iΩ_{m} are obtained as functions of the coherence length κ^{1/2} (κ being the wavenumber mismatch gradient), the plasma length L, and the basic gain length L_{0}. Where numerical results are available, they agree with the eigenvalues from the formulae to within 10% or better. The mth mode appears if, and only if, the inequality a_{m}L_{0}<κ^{1/2}<b_{m}L holds, where a_{m} and b_{m} are certain eigenvalues which, respectively, increase and decrease with m. The first part of the inequality determines the threshold pump intensity, whereas the second part defines a starting length.
 Publication:

Physics of Fluids
 Pub Date:
 June 1979
 DOI:
 10.1063/1.862703
 Bibcode:
 1979PhFl...22.1104F
 Keywords:

 Computerized Simulation;
 Coupled Modes;
 Free Electrons;
 Magnetic Control;
 Magnetic Field Configurations;
 Frequency Control;
 Mathematical Models;
 Resonant Frequencies;
 Tuning;
 Plasma Physics