# Faraday Effect - Mathematical Formulation

Mathematical Formulation

Formally, the magnetic permeability is treated as a non-diagonal tensor as expressed by the equation::

begin{align} mathbf{B}(omega) & = begin{vmatrix} mu_{1} & -i mu_{2} & 0\ i mu_{2} & mu_{1} & 0\ 0 & 0 & mu_{z}\ end{vmatrix} mathbf{H}(omega)\ end{align}

The relation between the angle of rotation of the polarization and the magnetic field in a transparent material is:

where

β is the angle of rotation (in radians)
B is the magnetic flux density in the direction of propagation (in teslas)
d is the length of the path (in meters) where the light and magnetic field interact
is the Verdet constant for the material. This empirical proportionality constant (in units of radians per tesla per meter) varies with wavelength and temperature and is tabulated for various materials.

A positive Verdet constant corresponds to L-rotation (anticlockwise) when the direction of propagation is parallel to the magnetic field and to R-rotation (clockwise) when the direction of propagation is anti-parallel. Thus, if a ray of light is passed through a material and reflected back through it, the rotation doubles.

Some materials, such as terbium gallium garnet (TGG) have extremely high Verdet constants (≈ −40 rad T−1 m−1). By placing a rod of this material in a strong magnetic field, Faraday rotation angles of over 0.78 rad (45°) can be achieved. This allows the construction of Faraday rotators, which are the principal component of Faraday isolators, devices which transmit light in only one direction.

Similar isolators are constructed for microwave systems by using ferrite rods in a waveguide with a surrounding magnetic field.

### Other articles related to "mathematical formulation, mathematical, formulation":

Lagrangian Mechanics - Conceptual Framework - Generalized Coordinates - Mathematical Formulation
... For example, for a simple pendulum of length ℓ, there is the constraint of the pendulum bob's suspension (rod/wire/string etc.) ... The position r depends on the x and y coordinates at time t, that is, r(t)=(x(t),y(t)), however x and y are coupled to each other in a constraint equation (if x changes y must change, and vice versa) ...
Paul Dirac - Career
... Dirac's attention was drawn to a mysterious mathematical relationship, at first sight unintelligible, that Heisenberg had reached ... weeks later, back in Cambridge, Dirac suddenly recognized that this mathematical form had the same structure as the Poisson Brackets that occur in the ... a more profound and significant general formulation of quantum mechanics than was achieved by any other worker in this field Dirac noticed an analogy ...
Galilean Scale Relativity - Mathematical Formulation
... The relativity of scales can be expressed by ratios. ...

### Famous quotes containing the words formulation and/or mathematical:

Art is an experience, not the formulation of a problem.
Lindsay Anderson (b. 1923)

What he loved so much in the plant morphological structure of the tree was that given a fixed mathematical basis, the final evolution was so incalculable.
—D.H. (David Herbert)