Abstract
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 a modified wavefront-sensorless (WFS) adaptive optical (AO) system where the well-known stochastic parallel gradient descent (SPGD) algorithm is extended with a-priori knowledge of the spatial and temporal statistics related to atmospheric turbulence. Here, a modal implementation of the correction algorithm allows us to exploit modal wavefront decomposition to decrease SPGD optimization complexity. We also propose an implementation of a modal decomposition based on Karhunen-Lo´eve polynomials instead of the common Zernike polynomials. Appropriate calibration of the deformable mirror is also presented. Performance evaluation of this modified wavefront-sensorless AO system is carried out in a realistic simulated turbulence environment and the results are compared against the traditional, zonal SPGD algorithms.