Fresnel rhomb

From Wikipedia, the free encyclopedia

A Fresnel rhomb is a prism-like device designed in 1817 by Augustin-Jean Fresnel for producing circularly polarized light. However, in contrast to a wave plate, the rhomb does not utilise birefringent properties of the material.

The rhomb (usually a right-parallelepiped) is shaped such that light entering one of the small faces is internally reflected twice: once from each of the two sloped faces before exiting through the other small face. The angle of internal reflection is the same in each case, and each reflection produces a 45° (π/4 radians) phase delay between the two linearly polarized components of the light. Hence on the first reflection, a linearly polarized beam will be elliptically polarized, and will emerge as circularly polarized on the second reflection.

For visible light and a glass rhomb (refractive index n ≈ 1.5), an internal reflection angle of incidence of 48° or 54.6° is required.

[edit] See also

• Fresnel equations

[edit] External link and references

• Hecht, E. (1987). Optics: Second Edition. Massachusetts: Addison-Wesley Publishing Company, Inc. ISBN 0-201-11611-1
• http://physics.kenyon.edu/EarlyApparatus/Polarized_Light/Fresnels_Rhomb/Fresnels_Rhomb.html