Figure 3 - Experimental setup.
From the following article
Geometrodynamics of spinning light
Konstantin Y. Bliokh, Avi Niv, Vladimir Kleiner & Erez Hasman
Nature Photonics 2, 748 - 753 (2008) Published online: 23 November 2008
doi:10.1038/nphoton.2008.229
A laser light beam enters the glass cylinder at a grazing angle through the input prism, coils along the cylinder surface, and leaves it by means of the output prism. The liquid-crystal variable retarder (LCVR) is used for generating and switching between the circularly polarized modes, whereas the quarter-wave plate (QWP) and polarizer P2 are intended for measurement of the Stokes parameters. The inset shows a real picture of the spiral light beam inside the cylinder.
