Metallic Coated Mirrors for the Infra-red
Gold
or silver coated mirrors make excellent broadband infra-red reflectors.
They are insensitive to polarization and angle of incidence.
Bare
gold or silver has a reflectance in excess of 99% throughout the IR spectrum but
they are soft and easily scratched. The
metallic films can be protected with a thin layer of silicon dioxide with only a
slight degradation of reflectance. Alternatively
an enhanced reflectance multi-layer dielectric coating may be applied.
For use with a helium-neon alignment beam a dual wave silver coating may
be used.
Silicon
is used as the substrate material in order to provide a stable flat surface,
which will dissipate any residual transmitted energy.
Typical
diameters offered are: 6.35, 12.7, 15.2, 19.1, 25.4, 27.9, 38.1, 50.8 and 63.5
mm.