Effect of atmospheric factors on the delivery of repetitively-pulsed CO2-laser radiation energy along paths in the surface layer of the atmosphere

<title>Feasibility analysis of bright-speckle algorithm of compensation for turbulent wandering of a laser beam</title>

“…In the experiments, the atmospheric turbulence was simulated by using two imitators (IM1 and IM2) resulting both in the largescale beam distortions that caused wandering of the beam over the receiver with an angular amplitude of ±λ/D (IM1) and in small-scale distortions that induced speckling of the beam (IM2). The imitators were placed in the beam propagation path by such manner that its total effects simulated the beam distortions that are accumulated by the beam in propagating through the near-land atmosphere range of 3-km length with the turbulence of C n 2 ~ 10 -13 m -2/3 [3]. The results show that the efficiency of the radiation delivery depends on the type of beam aberrations that being brought in the beam.…”

“…∆ θ , 10 -6 radian that was employed in the experiments by [3], when the range length was 240 m, the illuminating beam radius was of w = 65 mm, and the beam was focused at the distance of 240 m. The turbulence was simulated by the use of two optical imitators of the beam distortions by such a way that C n 2 ~ 2×10 -12 m -2/3 and β 0 = 0.309, and that the received intensity distribution matched the experimentally obtained field [3] most closely. As it can be seen, the width of the normalized covariance of the speckled field is equal to 10 -4 radian by e -1 level of the function drop, and it is of 5×10 -5 radian by the level of 0.9.…”

“…The latter means that sufficient de-correlation of the fields will exist, if the scanning angle difference exceeds 10 -4 radian, or if the non-coincidence of spatial directions of the probe and operation beams exceeds 10 -4 radian. In the figure 3 b, the normalized covariance of the received fields, recalculated for the conditions of the experimental investigation of laser beam propagation through real atmosphere range of 3-km long [3], is also shown as a function of ∆ θ . The curve is obtained for the following conditions: the illuminating beam radius is of 25 cm, L = 3 km, C n 2 = 2×10 -13 m -2/3 , that corresponds to β 0 = 1.584.…”