Other Effects
Certain nonlinear optical phenomena such as the electro-optic effect cause a variation of a medium's permittivity tensor when an external electric field is applied, proportional (to lowest order) to the strength of the field. This causes a rotation of the principal axes of the medium and alters the behaviour of light travelling through it; the effect can be used to produce light modulators.
In response to a magnetic field, some materials can have a dielectric tensor that is complex-Hermitian; this is called a gyro-magnetic or magneto-optic effect. In this case, the principal axes are complex-valued vectors, corresponding to elliptically polarized light, and time-reversal symmetry can be broken. This can be used to design optical isolators, for example.
(A dielectric tensor that is not Hermitian gives rise to complex eigenvalues, which corresponds to a material with gain or absorption at a particular frequency.)
Read more about this topic: Crystal Optics
Famous quotes containing the word effects:
“Let us learn to live coarsely, dress plainly, and lie hard. The least habit of dominion over the palate has certain good effects not easily estimated.”
—Ralph Waldo Emerson (1803–1882)
“to become a pimp
Or deal in fake jewelry or ruin a fine tenor voice
For effects that bring down the house could happen to all
But the best and the worst of us . . .”
—W.H. (Wystan Hugh)