Figure 2
From: Singular observation of the polarization-conversion effect for a gammadion-shaped metasurface

Experimental setup of the Mueller matrix ellipsometer, where P and A are polarizers and QG and QA are quarter-wave retarders.
(a) Optical setup for measuring the polarization properties of the first-order transmitted diffraction of the nanostructure with gammadion shape. (b) Optical setup for measuring the polarization properties of the first-order reflected diffraction of the nanostructure with gammadion shape.