Modal vs. zonal wavefront-sensorless adaptive optics for free-space laser communications

Atmospheric effects limit the performance of any electro-optical system. Tasks such as laser communication and delivery of directed energy are significantly affected by turbulence and refraction. A correction of atmospheric effects on the propagation of light can be done by adaptive optics (AO). Unconventional wavefront sensing strategies are being developed to provide alternatives for measuring the wavefront deformation of a laser beam propagating through strong turbulence and/or along a horizontal-path. In this paper we present results from two "wavefrontsensorless" approaches: stochastic parallel gradient descent (SPGD) and its modal version (MSPGD).