Drawing of a <a href="https://en.wikipedia.org/wiki/Poincar%C3%A9_sphere" class="extiw" title="en:Poincaré sphere">Poincaré sphere</a>, which illustrates the space of possible polarisations of electromagnetic waves. The sphere is drawn with three great circles, labels for six basic polarisations H (linear horizontal), V (linear vertical), D (linear diagonal), A (linear antidiagonal), R (right-hand circular) and L (left-hand circular) and images of the polarisation vectors for each. Additionally the coordinate system of Stokes vectors with components S₁, S₂ and S₃ is drawn in the center of the sphere.
<a href="//commons.wikimedia.org/wiki/User:Geek3" title="User:Geek3">Geek3</a>
CC BY 3.0
<span class="int-own-work" lang="en">Own work</span>