Effect of diffraction on reflector on the enhancement of the mean and variance of reflected wave intensity

Abstract

The results of experimental study of the mean and variance of intensity of laser beam after double passage in turbulence are presented. The experiments were held in the artificial turbulent medium created with the use of the laboratory convectional generator of turbulence. The pathlength in measurements equaled 2 m, the refractive index structure constant C<SUB>n</SUB><SUP>2</SUP> ranged up to about 5 (DOT) 10<SUP>-11</SUP> cm<SUP>-2/3</SUP>. As a reflector the plane mirror was used and measurements were carried out at different sizes of mirror both on correlated path (when incident and returned waves pass along the same pathway) and in the case of considerable spacing their pathways. The mean intensity on the correlated path, as compared with uncorrelated one, is shown to increase when the reflector dimensions are multiple of even number of Fresnel zones and to decrease when dimensions are multiple of odd number of zones. Intensity relative variance is maximal if reflector diameter multiples to integer of Fresnel zones m and is minimal for the mirror sizes multiple to (m + 0.5) Fresnel zones.