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18 August 2005 Direct wavefront sensing for atmospheric adaptive optics in strong scintillation
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Conventional adaptive optics (AO) systems using gradient wavefront sensors and linear least-squares reconstructors, perform very poorly when light has propagated through strong atmospheric turbulence. This is due to vortices in the wavefront that cannot be reconstructed using the least-squares method. One solution to the problem is to use non-linear reconstructors, however a second solution is to use direct wavefront sensors that circumvent the reconstruction problem. Direct wavefront sensors are simple self-referencing interferometers that directly measure the phase difference between a reference beam and an aberrated one. In this study the viability of a point-diffraction interferometer for a closed-loop atmospheric AO system was tested. A point-diffraction interferometer was built using a modified Mach-Zehnder set-up. The system was used in closed-loop using a ferroelectric SLM to produce the aberrated wave after correction. The SLM was used to emulate a corrective device that corresponded to a square, 12x12, piston-only segmented mirror with a stroke of ±π. Its performance was tested for the case of atmospheric turbulence aberrations. Both uniform intensity, and scintillated cases were looked at. The investigation showed, through simulation and experiment, that the point-diffraction interferometer worked in closed-loop operation in both uniform intensity and scintillated aberrations. Its robustness in the presence of phase discontinuities makes it a promising option for wavefront sensing in strong scintillation.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
James Notaras and Carl Paterson "Direct wavefront sensing for atmospheric adaptive optics in strong scintillation", Proc. SPIE 5894, Advanced Wavefront Control: Methods, Devices, and Applications III, 58940P (18 August 2005);

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