Near infrared (0.9-2.5 
m) imaging polarimetry
of large fields of view (>1 arcmin) with
sub-seeing image elongation can be best performed using Wollaston prisms
manufactured with AgGaS
or LiYF
.
From the optical point of view
the best material is AgGaS
because it has larger birefringence
and smaller chromatism. However, YLF may be practically more convenient
because of its lower refractive index (
and similar
to optical cements), better thermo-mechanical properties and lower price.
New measurements of the transmittance of Calcite at at 77 K
indicate that CaCO
cannot be used for
applications at wavelengths 
m in astronomical
polarimeters.