Encyclopedia > Birefringence

  Article Content


Birefringence, or double refraction, is the division of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on the polarization of the light. This is explained by assigning two different refractive indices to the material for different polarizations. The birefringence is quantified by:
<math>\Delta n=n_e-n_o</math>
where <math>n_o</math> is the refractive index for the ordinary ray and <math>n_e</math> is the refractive index for the extraordinary ray.

More generally, an anisotropic dielectric material has a dielectric constant that is a rank-2 tensor (3 by 3 matrix). A birefringent material corresponds to the special cases of a real-symmetric dielectric tensor ε with eigenvalues of <math>n_o^2</math>, <math>n_o^2</math>, and <math>n_e^2</math> along the three orthogonal principle axes of polarization. (Or, sometimes, only two axes are considered, corresponding to a single propagation direction.)

(In principle, birefringence could also arise in magnetic, not dielectric, materials, but substantial variations in magnetic permeability are rare at optical frequencies.)

See also crystal optics.

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article
U.S. presidential election, 1804

... Clinton (162) Charles C. Pinckney[?] 14 Federalist Rufus King (14) Other elections: 1792, 1796, 1800, 1804, 1808, 1812, 1816 Source: U.S. Office ...

This page was created in 27.9 ms