The Y is magnified by the Ronchi grating as an effect of Moiré aliasing.
Projections of optical vortices.
The first photo is the combination of the Ronchi and fork gratings 90° out of phase.
The other is the result when only the Ronchi grating is used.
The vortices projected onto a .25" grid. The close-ups are of vortices of topological charge 1, 2 and 3, respectively.
For other research (fiber optics) pictures, see my
WISE web page.
My poster at the Research Celebration, 21 April 2004