Zero Order Quartz Waveplates
Bi-refringent
materials such as crystal quartz can be used to retard the passage of the
extra-ordinary ray resulting in a change of phase difference between the s–
and p– states of polarisation. By
controlling the thickness of plates of quartz it is possible to achieve precise
amounts of retardation. A quarter-wave plate has a net retardation of p/2 and
changes the polarisation state from linear to circular or vice-versa.
A half-wave plate has a net retardation of p
and rotates the plane of
polarization by 90°.
These
waveplates are quartz plates with known amounts of retardation at a specific
wavelength. Two such plates of opposite retardation are joined together so that
the net retardation is of true zero-order.
The retardation tolerance is λ/500.
The plates are joined by cementing, optically contacting or may be
air-spaced. Cemented and optically contacted waveplates are available
un-mounted or mounted in a metal cell. Air-spaced
waveplates must be mounted.
Waveplates
are normally provided as circular plates of 10, 20 or 30 mm diameter, providing
a clear aperture of 8, 18 and 25 mm respectively when mounted.
Inch sizes can also be supplied.