At the top of the illustration to the right, is the circularly polarized light after it leaves the wave plate, and again directly below it, for comparison purposes, the linearly polarized light that entered the quarter-wave plate. The vectors leading from the axis to the helix represent how the magnitude and direction of the electric field varies for a given plane along the direction of travel. Note now how the magnitude of the field is constant while its direction steadily changes. The blue and green lines are projections of the helix onto the vertical and horizontal planes respectively and represent how the electric field changes in the direction of those two planes. Notice how the rightward horizontal component is now one quarter of a wavelength behind the vertical component. It is this quarter of a wavelength phase shift that results in the rotational nature of the electric field. It is significant to note that when the amplitude of one component is at a maximum the magnitude of the other component is always zero. This is the reason that there are helix vectors which exactly correspond to the maximums of the two components.
This image was created using the open source program Inkscape. If you open it using that program the image will still be divided into layers and you will have access to information used to create it. If you need to alter it I would suggest first going to my Wikimedia User page at Dave3457 where information is gathered and other related images are listed.
