Dielectric or Metal: Which Mirror Coating is Better?
Firstly, if your application requires that certain wavelengths of light transmit through the optical surface, your choice is clearly a purely dielectric film. Metal coatings typically have no transmission. Yes, there are certain applications, typically beam combiners, where thin metal layers are used allowing the light to both transmit and reflect but even in these applications, often a pure dielectric film is superior. Where metal films shine is when the reflection wavelength band required by your application is so wide that producing the required reflection with a dielectric film is not feasible due to the impractically large number of layers required. Typically, films of more than 100 layers become quite expensive and you can expect long lead times. What are Optical Mirror Coatings? Optical mirror
