A crystal with only one optic axis is called a uniaxial crystal.
2.
Birefringence is the difference between two principal indices of refraction of a uniaxial crystal.
3.
A uniaxial crystal is isotropic within the plane orthogonal to the optic axis of the crystal.
4.
A uniaxial crystal is " positive " if n e > n o and " negative " if n e o.
5.
Aligned nematics have the optical properties of uniaxial crystals and this makes them extremely useful in liquid crystal displays ( LCD ).
6.
"' Lithium iodate "'( LiIO 3 ) is a negative uniaxial crystal for nonlinear, acousto-optical and piezoelectric applications.
7.
For a uniaxial crystal, this is the " optic axis ", the " z " direction according to the above construction.
8.
Thus there is no axis around which a rotation leaves the optical properties invariant ( as there is with uniaxial crystals whose index ellipsoid " is " a spheroid ).
9.
If they belong to uniaxial crystals they show a dark cross or convergent light between crossed nicols, the bars of which remain parallel to the wires in the field of the eyepiece.
10.
In a uniaxial crystal, different polarization components of a beam will travel at different phase velocities, " except " for rays in the direction of what we call the optic axis.
