Experimental and numerical analysis of atmospheric propagation of high energy laser

Abstract

The transmission of high power laser radiation through the atmosphere is influenced by turbulent motion of the air. As a result the beam experiences an alteration regarding its position and its distribution, which increases with increasing propagation length. In order to analyze the atmospheric influence on the laser beam propagation a disk laser with a maximum output power of 6 kW and a wavelength of 1.03 µm is operated on a 130 m long free transmission laser test range in Lampoldshausen. The test range is equipped with a variety of sensors, which continuously monitor the current status of the weather conditions. Power sensors and camera systems at the beginning and the end of the test range measure the laser beam parameters before and after propagation. The experimental results are compared with a numerical analysis of the laser beam propagation performed by the software TALAP (Turbulent Atmosphere and Laser Beam Propagation), developed at the Institute of Technical Physics of DLR. It is based on the Kolmogorov turbulence model, which considers turbulent cells of different scale sizes. First measurements of power transmission, diameter of the laser beam and variations of its center of gravity are performed on a sunny and on a rainy day. The results show a good correlations to the measurements of the turbulence strength and the visibility. A comparison to the numerical analysis has shown coincidences. Future measurements will be performed at different weather conditions and seasons. Experimental results will be used to modify the simulation software, if necessary.