Estimation of turbulent and thermal blooming degradation and required characterization of adaptive system

Boris V. Fortes; Vladimir P. Lukin

doi:10.1117/12.356977

3 August 1999 Estimation of turbulent and thermal blooming degradation and required characterization of adaptive system

Boris V. Fortes, Vladimir P. Lukin

Proceedings Volume 3706, Airborne Laser Advanced Technology II; (1999) https://doi.org/10.1117/12.356977
Event: AeroSense '99, 1999, Orlando, FL, United States

Abstract

A laser beam propagating in the atmosphere are influenced simultaneously by thermal blooming and turbulence that results in aberrations of a focal spot. Character of thermal blooming depends not only on atmospheric conditions but also on beam power and velocity of a target. Turbulent aberrations prevail at large sped of scanning, from this point of view they are more important. In the previous papers it was pointed out that thermal aberrations of laser beams decrease sharply as the object velocity increases. If Mach number is greater than unity and laser power is not too great, the influence of thermal blooming is negligible. Effectiveness of phase correction for thermal blooming increases at increase of scanning velocity, because in this case the thermal lens is placed near the transmitting aperture. On the contrary, effectiveness of correction for turbulent aberrations decreases when the object velocity increases. Turbulent aberrations do not depend on sped of angular scanning but in the case of a moving object the requirements to the adaptive system bandwidth are higher than that for a motionless target. For beams with power about 500 kW and wavelength (lambda) equals 1.315 micrometers on the upper atmosphere paths turbulent aberrations are always stronger compared to thermal blooming even for motionless targets. So if the correction for turbulent aberrations is possible, the correction for thermal blooming is possible too.

Citation Download Citation

Boris V. Fortes and Vladimir P. Lukin "Estimation of turbulent and thermal blooming degradation and required characterization of adaptive system", Proc. SPIE 3706, Airborne Laser Advanced Technology II, (3 August 1999); https://doi.org/10.1117/12.356977

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