Fast and Slow Rays
| Propagation direction |
Ordinary ray | Extraordinary ray | ||
|---|---|---|---|---|
| Polarization | neff | Polarization | neff | |
| z | xy-plane | n/a | n/a | |
| xy-plane | xy-plane | z | ||
| xz-plane | y | xz-plane | ||
| other | analogous to xz-plane | |||
For a given propagation direction, in general there are two perpendicular polarizations for which the medium behaves as if it had a single effective refractive index. In a uniaxial material, rays with these polarizations are called the extraordinary and the ordinary ray (e and o rays), corresponding to the extraordinary and ordinary refractive indices. In a biaxial material, there are three refractive indices α, β, and γ, yet only two rays, which are called the fast and the slow ray. The slow ray is the one for which the material has the highest effective refraction index.
For a uniaxial material with the z axis defined to be the optical axis, the effective refractive indices are as in the table on the right. For rays propagating in the xz plane, the effective refractive index of the e polarization varies continuously between and, depending on the angle with the z axis. The effective refractive index can be constructed from the index ellipsoid.
Read more about this topic: Birefringence
Famous quotes containing the words fast, slow and/or rays:
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One little sandpiper and I;
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The wild waves reach their hands for it,
The wild wind raves, the tide runs high,
As up and down the beach we flit—
One little sandpiper and I.”
—Celia Thaxter (”Laighton”)
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“‘Line in nature is not found;
Unit and universe are round;
In vain produced, all rays return;
Evil will bless, and ice will burn.’
As Uriel spoke with piercing eye,
A shudder ran around the sky;”
—Ralph Waldo Emerson (1803–1882)