Adaptive Laser Compensation for Aero-Optics and Atmospheric Disturbances
نویسندگان
چکیده
Performance of adaptive optics (AO) compensation for beam control is quantified via wave-optical propagation, sensing, and control methods using wind tunnel measurements of aero-optical disturbances in addition to Kolmogorov turbulence distributed over a laser path. For Kolmogorov turbulence the residual phase variance scales as (fG/f3dB) , where fG is the Greenwood frequency for the propagation path 2 and f3dB is the error-rejection bandwidth of the classical AO control. It is shown that the residual phase variance with classical AO control, when normalized to the open-loop, scales as (fA/f3dB) γ , where γ is an arbitrary power and fA is a characteristic frequency of the aero-optical disturbance determined from a linear fit of the compensation data with increasing bandwidth. AO system latency degrades performance, especially with high-bandwidth control. When operating at a fixed but modest sampling frequency with appreciable latency, AO compensation performance can be significantly enhanced by application of an adaptive control augmentation based on lattice filtering of the residual wavefront sensor gradients, as was implemented in the wave-optics simulations. A classical controller operating at 200 Hz bandwidth with > 400 μsec latency has a limited ability to compensate the aero-optical and free-stream disturbances. By application of the adaptive feed-forward control, laser peak irradiance is shown to increase by a factor of 2.5 or more compared to classical AO feedback control.
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