Perturbation growth by thermal blooming in turbulence

Technical Report · Wed Jan 04 04:00:00 EST 1989

DOI:https://doi.org/10.2172/6993565· OSTI ID:6993565

Karr, T J; Morris, J R; Chambers, D H; Viecelli, J A; Cramer, P G

The stability of a phase-compensated laser beam propagating in a turbulent absorbing fluid is considered. Small-scale transverse optical perturbations from turbulence and noise grow in thermal blooming by two instabilities: the uncompensated stimulated thermal Rayleigh scattering instability, and the closed-loop instability. Linearized perturbation theory is used to calculate the electric field spectrum as a Taylor series in time and as superposition of stable and unstable modes. The method is applicable to fluids with arbitrary parameter variations along the path. Compensated perturbations grow exponentially, and uncompensated ones grow quasi-exponentially. The instability growth is in good agreement with numerical simulations of full nonlinear thermal blooming. If the growth rate exceeds the damping rate from other phenomena then the perturbations grow until limited by nonlinear saturation, at which point the beam is significantly degraded. At saturation the laser beam spontaneously breaks into small-scale transverse structures such as filaments or ribbons. 18 refs., 2 figs.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• Sponsoring Organization: DOD
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6993565
• Report Number(s): UCID-21702; ON: DE90010759
• Country of Publication: United States
• Language: English

Related Subjects

656003* -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COHERENT SCATTERING
COMPUTERIZED SIMULATION
ELECTROMAGNETIC RADIATION
FLUIDS
FOCUSING
INSTABILITY
INSTABILITY GROWTH RATES
LASER RADIATION
OPTICAL PROPERTIES
PERTURBATION THEORY
PHYSICAL PROPERTIES
RADIATIONS
RAYLEIGH SCATTERING
RAYLEIGH-TAYLOR INSTABILITY
REFRACTIVITY
SCATTERING
SIMULATION
TURBULENCE
WAVE PROPAGATION