Polarization of light by internal reflection: Fresnel rhomb.

White light from a carbon arc passes through a Polaroid at 45 deg , then passes through a Fresnel Rhomb, reflecting internally twice, and emerges circularly polarized (CP). If the CP light then passes through a second Polaroid, the beam will not be extinguished no matter how the Polaroid is rotated. However, if a quarter-wave plate is inserted into the CP beam, then the CP light will emerge plane polarized, and the second Polaroid can then be used to analyze the beam (I.E.: the beam will be extinguished at some point when the second Polaroid is rotated). Looking at Figure 1, if plane polarized light hits the left side of the Fresnel Rhomb with the plane of vibration at an angle of 45 deg with-respect-to the plane of the paper, then the beam reflects internally in the rhomb at point 'A' with a phase change of 45 deg , making the light elliptically polarized, and then reflects again at 'B' with another phase change of 45 deg , making the light circularly polarized. Polarization of light by internal reflection: Fresnel rhomb. Ref.: Fundamentals of Physical Optics,-Jenkins & White,1st Ed., p.396