Design and experiment of a soft-edge aperture with high light energy utilization efficiency and uniformity

Soft-edge apertures can be used to suppress the diffraction effect to achieve high beam quality. In this study, an optimal design theory was proposed to design a serrated soft-edge aperture (SSA) that could produce a beam with high light energy utilization efficiency and uniformity. Two parameters of the peak-to-average ratio (PAR) and the light energy utilization efficiency were introduced as the criteria for evaluating the soft-edge aperture (SA) performance. By analyzing the influence of the shape, number, and height of the serrated structure on the beam propagation performance, the relationship between the PAR, light energy utilization efficiency, and the structural parameters of the aperture were established. After that, an optimal design method of the SSA was proposed, based on the theory of Fresnel diffraction. The designed SSA was fabricated by lithography, and an optical configuration was constructed to test the effect of the aperture. In the experiment, the light energy utilization efficiency is greater than 92%, the PAR is less than 1.4, and the root mean square error of the PAR curve is 0.3502, indicating that the beam maintains high light energy utilization efficiency and uniformity during propagation.