Focused Beam and Atmospheric Coherence Measurements at 106 μm and 063 μm

Measurements of focused spot characteristics and the atmospheric modulation transfer function (MTF) over a 5.4-km horizontal path with laser light at 10.6 microm and 0.63 microm are reported. The atmospheric coherence diameter has been shown to be proportional to lambda(6/5) in verification of theory. The atmospherically degraded long-exposure 10.6-microm spot shape was Gaussian, and the spot wander exhibited a stronger dependence on turbulence strength relative to spot blur than was theoretically predicted. The diurnal cycle of the 10.6-microm spot characteristics and of the 10.6- and 0.63-microm atmospheric MTF's under clear-sky conditions were also observed.