Dielectric mirrors vs. metallic mirrors – what are the differences?

Metallic mirrors (aluminium, silver, gold): reflection via a thin metal coating. Typically up to>98 % reflectivity in the visible range. Benefits: broadband (from UV to IR), low cost. Drawbacks: lower power handling, prone to oxidation (especially silver), reflectivity depends on angle of incidence. Dielectric mirrors: reflection via multi-layer glass coatings that reflect through interference. Typically > 99 % reflectivity in the optimized spectral range. Benefits: extremely high reflectivity, high power handling, no oxidation. Drawbacks: narrowband (optimized for a specific wavelength), more expensive. Our LS 50 is a dielectric mirror with > 96–98 % reflectivity in the 400–700 nm range.