Numerical Study on Micro-optical Vortex Generation with the Use of an Achromatic Nanostructured Phase Mask

We present the design and numerical evaluation of an achromatic, nanostructured vortex phase micro-optical mask and a numerical analysis of its optical function to generate fundamental charged optical vortex beams in the visible and near-infrared spectral regions. The nanostructured mask was designed using a pair of thermally compatible commercial glasses, enabling cost-effective production through an adapted stack-and-draw technique. An initial investigation was conducted on 20 μm-thick free-space achromatic vortex phase mask designs. The results confirmed successful vortex beam generation with a fundamental topological charge, with mode-conversion efficiencies reaching 100% at wavelengths of 542 nm and 773 nm. Furthermore, the mask demonstrated the ability to correct chromatic aberration, achieving over 90% mode-conversion efficiency across a broad spectrum (bandwidth of 416 nm) from 504 nm to 920 nm. These results highlight the potential of this achromatic nanostructured vortex mask for integrated broadband vortex beam generation in applications such as optical trapping, high-resolution microscopy, and laser micromachining