Protected Aluminum Mirror(Metallic Coatings)
·Broadband reflectors
·Not sensitive to polarization and incident angle
·Low damage threshold, can NOT be used on high power lasers
Metallic coatings make very broad bandwidth
reflectors. Usually it is best to protect the coatings with a durable dielectric
layer as they are very soft and susceptible to scratching. The efficiency of
metallic reflectors flls off at shorter wavelengths but this may be enhanced by
the application of a multi-layer dielectric thin film stack. The table shows
the reflectance of each of the metals without any protection or enhancement.
Protected metallic coatings have a
dielectric coating layer over the metallic layer to protect the coating from
being oxidized in the air or from scratched.
For enhanced metallic coatings, a tack of
dielectric layers are added on the metallic coating to increase reflectance for
a particular wavelength range.
Coating code &nbs…