Multiple 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 (2k+1)p/2
and changes the polarisation state from linear to circular or vice-versa.
A half-wave plate has a net retardation of (2k+1)p and rotates the plane
of polarisation by 90°.
These
waveplates are quartz plates with known amounts of retardation at a specific
wavelength. The retardation tolerance is λ/500.
They are available un-mounted or mounted in a metal cell.
It
is also possible to provide dual wavelength waveplates, which transmit two
harmonic wavelengths so they emerge with crossed linear polarisation.
These have half wave retardation at λ1 and one wave
retardation at λ2. A
full waveplate has a net retardation of 2kp and rotates the plane of
polarisation by 180°. A half-wave
plate has a net retardation of (2k+1)p and rotates the plane of polarisation by
90°.
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.