To simulate in the laboratory the influence that the turbulent atmosphere has on light beams, we introduce a practical method for generating atmospheric wavefront distortions that considers digital holographic reconstruction using a programmable binary micro-mirror array. We analyze the efficiency of the approach for different configurations of the micro-mirror array and demonstrate the benchtop technique experimentally. Though the mirrors on the digital array can only be positioned in one of two states, we show that the holographic technique can be used to device a wide variety of atmospheric wavefront aberrations in a controllable and predictable way for a fraction of the cost of a phase-only SLM.
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
Holographic wavefront sensing (HWS) has been proposed as a solution to overcome the main limitations that traditional Shack-Hartmann sensors: low bandwidth and sensitivity to scintillation. However, the accuracy of HWS is compromised due to presence of intermodal crosstalk effects which limit the sensor's performance considerably. In this paper, we propose the use of the Karhunen-Loève (K-L) functions as a new basis in which the aberrated wavefronts are decomposed and we provide experimental results of the measured intermodal crosstalk. We evaluate the sensor's performance in the presence of emulated atmospheric turbulence and provide a comparison between sensors based on either Zernike or K-L decompositions. Additionally, we show first experimental results from a HWS using K-L for measuring simulated atmospheric turbulence.
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