Aero-optical effects in free-space laser communications

When a laser beam is transmitted from an airborne platform, it must first pass through a relatively thin region of the turbulent flow in the immediate vicinity of the airplane. Unsteady density variations present in the turbulent flow will imprint spatial/temporal variations on the otherwise planar outgoing wavefronts. These variations in wavefronts will force the beam to move, change its shape and even break into several spots on a distant target. These aero-optical effects [1,2], even in the absence of any atmospheric optical distortions, might significantly degrade a performance of any free-space, laser-based airborne systems at subsonic, transonic or supersonic speeds.