Removal of Zero-Order Beam Interference using Dammann Grating Grayscale Map

Zero-order beam interference is generated at the focal plane when the liquid crystal spatial light modulator (LCSLM) is loaded with a computer-generated hologram (CGH) during laser beam splitting. To address this issue, we proposed to load a Dammann grating grayscale map to LCSLM using phase extinction interference, thereby removing zero-order beam interference. Based on the simulated annealing algorithm, the set of phase turning points was solved; simulations were performed in VirtualLab; and a script for generating Dammann grating grayscale maps was written using MATLAB software. Consequently, a verification system was built based on a liquid crystal on silicon spatial light modulator (LCOSSLM), and its modulation effect was tested. The results show that the zero-order beam interference is removed in the CCD field of view by loading the Dammann grating grayscale map for laser beam splitting. Moreover, the actual beam-splitting effect is close to that observed in the simulation results. Furthermore, the beam-splitting uniformity under one-dimensional five-beam splitting reaches 97. 190%, which is better than the modulation effect of the grating CGH generated by the GSW algorithm. When the focal distance is large, effects of one-dimensional two-and seven-beam splitting are observed with beam-splitting uniformity levels of 98. 453% and 96. 820% respectively. The two-dimensional beam splitting is also observed with a measured beamsplitting uniformity of 95. 436%. In addition, no zero-order beam is observed in the CCD field of view.