# Fast fabrication of optical vortex generators by femtosecond laser ablation

## TL;DR

This paper demonstrates a rapid method for fabricating micro-optical vortex generators using femtosecond laser ablation on gold films, achieving precise grating structures suitable for optical applications.

## Contribution

It introduces a fast, efficient femtosecond laser ablation technique for creating optical vortex generators with high precision and thermal stability.

## Key findings

- Fabrication time for q-plates is approximately 1 minute.
- Achieved grating period of 0.8 micrometers and groove width of 250 nm.
- Efficiency of spin-orbital conversion is around 3%.

## Abstract

Fast fabrication of micro-optical elements for generation of optical vortex beams based on the q-plate design is demonstrated by femtosecond (fs) laser ablation of gold film on glass. Q-plates with diameter of ~0.5 mm were made in ~1 min using galvanometric scanners with writing speed of 5 mm/s. Period of gratings of 0.8 micrometers and groove width of 250 nm were achieved using fs-laser ablation at 343 nm wavelength. Phase and intensity analysis of optical vortex generators was carried out at 633 nm wavelength and confirmed the designed performance. Efficiency of spin-orbital conversion of the q-plates made by ablation of 50-nm-thick film of gold was ~3%. Such gratings can withstand thermal annealing up to 800C. They can be used as optical vortex generators using post-selection of polarisation.