Linear theory of uncompensated thermal blooming in turbulence
Abstract
A linearized theory of small perturbations in thermal blooming gives a surprisingly accurate description of the initial evolution of a plane wave propagating through an absorbing fluid medium. In the case of constant absorption and fluid velocity, a sinusoidal perturbation of the optical field grows quasiexponentially at a rate determined by its Fresnel number and the accumulated OPD due to blooming. Perturbations with small transverse length scales grow more rapidly than those with large length scales. The evolution of the optical spectrum and Strehl ratio in the presence of optical turbulence is accurately described. The growth of the small scale fluctuations eventually leads to a drop in Strehl. More complicated cases with varying absorption and velocity profiles can be formally analyzed using a WKB approximation. Numerical simulations show growth suppression when the velocity varies along the optical path. These predictions from the linearized theory agree well with results from numerical simulations of the full nonlinear system and thus provides a standard for comparing different numerical codes.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 February 1989
 Bibcode:
 1989STIN...8928812C
 Keywords:

 Laser Outputs;
 Mathematical Models;
 Thermal Blooming;
 Turbulence;
 Wave Equations;
 Wave Propagation;
 Plane Waves;
 Predictions;
 Radiation Absorption;
 Lasers and Masers