Generation of high-order optical vortices using directly machined spiral   phase mirrors
  We report on the generation of high-order optical vortices by spiral phase mirrors. The phase mirrors are produced by direct machining with a diamond tool and are shown to produce high-quality optical vortices with topological charges ranging from 1 to 1000 at a wavelength of 532 nm. The direct machining technique is flexible and offers the promise of high-precision, large-diameter spiral phase mirrors that are compatible with high optical powers. 
Geoff Campbell, Boris Hage, Ben Buchler, Ping Koy Lam
physics.optics