Characterizing static aberrations in liquid crystal spatial light modulators using phase retrieval

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There is a significant fixed aberration in some commercial off-the-shelf liquid crystal spatial light modulators (SLMs). In a recent experiment we conducted to simulate the effects of atmospheric turbulence and correction schemes in a laboratory setting using such an SLM, this aberration was too strong to neglect. We then tried to characterize and correct the observed aberration. Our method of characterizing the device uses a measurement of the far-field intensity pattern caused by the aberration and processing based on a parameterized version of the phase retrieval algorithm. This approach uses simple and widely available hardware and does not require expensive aberration sensing equipment. The phase aberrations were characterized and compared with the manufacturer's published measurements for a similar device, with excellent agreement. To test the quality of our aberration estimate, a correction phase was computed and applied to the SLM, and the resulting far-field patterns were measured and compared to the theoretical patterns with excellent results. Experiments show that when the correction is applied to the SLM, nearly diffraction-limited far-field intensity patterns are observed. © 2007 Society of Photo-Optical Instrumentation Engineers.

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Optical Engineering