Adaptive Flattop Beam Shaping With a Spatial Light Modulator Controlled by the Holographic Tandem Method

This paper reports the realization of a closed-loop feedback system, which consists of a spatial light modulator controlled by the holographic tandem method, for adaptive far-field flattop beam shaping. The holographic tandem method iteratively adjusts the phase distributions to be written into the two different regions of a spatial light modulator so that the Gaussian beam can be converted into an annular flattop beam for better uniformity. The technique described in this paper can provide a promising convenient way to create the desired flattop intensity profile of a beam on a focal plane, which could be applied in applications involving laser fusion and laser precision machining.