  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.
