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9 September 2019 Nonmechanical beam-steering in reflective inverse diffusion
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Wavefront shaping is a technique that uses phase or amplitude modulation to create desired wavefronts on light in optical systems. Wavefronts which are properly conjugated will refocus after reflection from a rough surface. This refocusing effect is called reflective inverse diffusion. There currently are two different wavefront shaping techniques used to achieve reflective inverse diffusion: iterative methods and matrix methods. Iterative methods find one phase front which allows for reflected light to be focused at a single, specific position, with results that are immediately available and continuously improving. Matrix methods calculate the complex matrix which describes the rough surface and allow for reflected light to be be refocused at many positions after reflective inverse diffusion and at multiple spots simultaneously. However, matrix methods are susceptible to decreased performance in a noisy system, and their results are not available until the entire matrix is measured. A new alternative method for reflective inverse diffusion combines non-mechanical beam steering principles with an iterative method’s phase front, giving it the multiple-spot capabilities of matrix methods. Utilizing an optical Fourier transform relationship in the reflective inverse diffusion setup, the shift theorem of Fourier transforms creates phase tilts at the sample on top of the conjugating phasefront when the phasefront from the SLM is translated in position. The phase tilts at the sample steer the reflected focused beam. Translations of an iterative method’s phase front using circular shifts steer the reflected spot at the cost of decreased enhancement with a larger shift.
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Eric K. Nagamine, Kenneth W. Burgi, Samuel D. Butler, and Michael A. Marciniak "Nonmechanical beam-steering in reflective inverse diffusion", Proc. SPIE 11107, Laser Beam Shaping XIX, 1110706 (9 September 2019);

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