Compensation for the spatial periodic modulation of the near-field beam with an improved iterative weight-based method

An improved iterative weight-based method is studied to compensate for the spatial periodic modulation (SPM) of the near-field beam. Based on the beam angular spectrum transmit formula (ASTF), the required phase that compensates for the intensity distribution of the incident SPM beam is iterated by this algorithm, which can contribute to improve the uniformity and quality of the output near-field beam. The experimental results show that the similarity value ε is improved from 0.9878 to 0.9947 and is getting closer to 1. The modulation degree M of the output near-field beam is decreased from 1.3631 to 1.3401 and the contrast degree C is decreased from 0.3018 to 0.2635 by using the liquid-crystal spatial light modulator (SLM). This indicates that the experiment verifies the feasibility of this iterative method to compensate for the SPM of the near-field beam.