Re: First-surface mirrors don't polarize, do they?


Yikes. Neither of those sounds good for mirrors intended for use with
a variety of wavelengths, 200 to 2500nm in the case of this spectrometer.
I suppose actual silver would tarnish. Is it still used?

To cover those wavelengths, the best all around reflecting material is
Aluminum. Usually, a very thin layer of MgF2 or LiF is used to help slow
oxidation, but the mirrors are still extremely fragile.
Silver should NEVER be used to cover those wavelengths. Reflection drops off
drastically in the UV. As a matter of fact, it's a dielectric somewhere down
there (forget the wavelength right now.. think it's somewhere around 270nm).

As for enhanced aluminum mirrors, they are great for fairly narrow
wavelength regions. But, in trying to cover very wide wavelengths, an
extremely large number of layers would be required. Once you get that many
layers on the substrate, you may as well not even bother with the aluminum.



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Relevant Pages

  • Re: why are toned Morgans worth more?
    ... on the surface of the coin. ... Basically silver tarnishes because of sulphur in the atmosphere or ... Silver sulphide is black - heavily tarnished coins go black. ... A little thicker and some wavelengths will be 'out of phase' ...
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  • Re: Double transmission peak narrow band filter?
    ... Another way is to spring for a good thin-film program, design a bandpass, ... layers, and the precision will be just as demanding. ... wavelengths to end up with broadband high reflectivity. ...
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