AUTHORS:

Nguyen H.T., Kasztelanic R., Le H.V., Thi H.T., Pysz D., Nguyen V.P., Hoang V.T., Omatsu T., Buczyński R.

ABSTRACT:

We report the development and characterization of a fractional nanostructured gradient-index (GRIN) vortex phase component for generating fractional optical vortex (OV) beams in the near-infrared. The element was fabricated using a modified stack-and-draw method, yielding a proof-of-concept mask with a thickness of 38μm and a 30 μm vortex core. The performance of the component was evaluated through both theoretical analysis and experiment. Optical measurements confirmed the formation of OV beams with integer and fractional topological charges between l= 3 and l= 4, exhibiting characteristic phase singularities and corresponding intensity structure, in good agreement with numerical simulations. The flat-surface geometry, broadband spectral response, and reproducible fabrication approach confirm the fractional nanostructured GRIN vortex phase component as a compact and versatile platform for controllable vortex generation, with potential applications in optical tweezers, biological particle manipulation, optical communication, optical imaging, and laser-based material processing.

Journal of Physics-Photonics, 2026, vol. 8(2), art. 025007, doi: 10.1088/2515-7647/ae5d0d