Diamond-based deep ultraviolet vortex beam generation with suppressed higher-order diffractions

Optical vortices (OVs) with unique singular phase and orbital angular momentum are widely used in various applications including particle manipulation, microscopy, and imaging scenarios. Regardless, the undesired higher-order foci introduced by the conventional vortex lens such as spiral zone plates may lead to additional artifacts and thus degrade contrast sensitivity. In this endeavor, based on the typical trapezoidal contour matrix and the neural network-based inverse design approach, we propose an innovative single-focus OV lens termed trapezoidal spiral zone plates (TSZPs) to eliminate the higher-order foci which unavoidably exist in the conventional muti-foci lens. Considering the low thermal expansion of diamond materials, we have fabricated the TSZPs sample based on high-quality single-crystal diamond substrate using electron beam lithography. To verify the stable single-focus performance even under harsh environments of such optics, a demonstration experiment in the deep ultraviolet region has also been performed. These findings provide an avenue for improving the image performance of diamond-based optics in solar-blind imaging.