Glan Taylor Polarisers
Glan
Taylor polarisers utilize the high bi-refringence of natural crystal calcite to
produce a linearly polarised output from a laser beam of random polarisation. They consist of two prisms of calcite separated by an
air-space. They produce a high
degree of polarisation in the transmitted beam with an extinction ratio of 1 X
10-6. They have a
transmittance of over 88% and an 8° field of view.
Calcite
is available in several different grades. For
laser use, Glan Taylor polarisers must be made of laser grade calcite, which is
of high homogeneity, has few inclusions and shows no scattering when illuminated
with a helium neon laser beam. For
applications in the ultra-violet (from 220—350 nm) UV grade calcite should be
selected. For less demanding
applications it is acceptable to use either optical grade or standard grade
calcite. Optical grade shows no
scattering when viewed under a 40 watt incandescent lamp.
Standard grade shows some scattering.
Glan
Taylor polarisers normally supplied as square cross section prisms with an
aperture of 8, 10, 12, 15 or 20 mm. They
are mounted in an absorbing black potting compound within a metal cell.
Single
layer MgF2 anti-reflection coatings may be applied if required. These coatings provide a reflectance of less than 2% over a
range of 220-400 nm, 400-700 nm, or 700-1100 nm.