Lei Liu, Yesheng Gao, Xingzhao Liu
Control over both amplitude and phase of optical beams plays an important role in optics, especially in the field of optical trapping. Trapping particles needs optical beams with specified intensity distribution and desired phase distribution, so joint control over light beams with high precision is indispensable. In this paper, a novel joint amplitude and phase control method specially designed for high precision using a digital micromirror device (DMD) is proposed. An off-axis 4f-configuration and a pattern formation algorithm are required for the implementation of the proposed method. Getting DMD pattern by considering the correlations among all pixels guarantees the high precision but increases the computation complexity, which makes it difficult to realize. Thus we present a pattern formation algorithm based on mixed integer programming and its improved version with higher computing efficiency. Experimental tests have been conducted to verify the superior performance of the proposed method over the conventional methods, such as Lee holography and Superpixel method. Measured results and quantitative analyses show that the proposed method enables simultaneous and independent control over amplitude and phase of light beams with a higher precision and performs better when steepest phase gradients exist in the target field. What is more, vortex beam and line beam can be generated accurately by the proposed method.
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