UV to FIR
Gold, Silver, Aluminium, Rhodium and Platinum layers
reliable supplier to the optical industy for over 20 years
In many applications, the highest possible reflection is required. For mirrors in optical instruments, metallic coatings are therefore often the best choice because they increase the reflection of a surface. The different metals have advantages and disadvantages depending on the application, so the choice of material depends on the application. Gold, silver and aluminum are the most commonly used coating materials for manufacturing optical mirrors.
Each of these metals is particularly suitable for a specific spectral range. For example, gold mirrors are mainly used for infrared applications. Rhodium and platinum, on the other hand, are used when high stability of the metallic coatings is required due to aggressive environmental conditions. Our metallic coatings are applied using PVD methods. They are therefore low in layer stress and suitable for almost all materials.
Gold is the best material for all metallic coatings in the infrared range Infrared, however, it can only be used from a wavelength of 700 nanometers (nm). Since a gold coating is soft, it scratches easily. For this reason, the gold coating should be provided with a dielectric coating.
Gold is a precious metal and therefore does not tarnish, and is therefore stable over the long term. A gold coating can therefore also be used without a protective layer, for example in FTIR spectroscopy. Applications of metallic coatings with gold are infrared mirrors (measurement technology), laser mirrors (low power applications) as well as protective coatings (corrosion protection).
Wavelength | Angle of incidence | Reflection |
|---|---|---|
630-635 nm | 45° r-pole | 82,0 % ± 2,5 % |
1-2 µm | 45° r-pole | 95,0 % ± 1,0 % |
2 µm | 45° r-pole | 98,0 % ±0 ,5 % |
10,6 µm | 0° 45° s-pole 45° r-pole | 99,0 % ± 0,2 % 99,1 % ± 0,2 % 98,4 % ± 0,2 % |
Silver coatings have the highest reflection in the visible and infrared spectral range. However, due to the affinity of silver for some fractions of the air, this material tarnishes easily. A protective coating can significantly slow down this process, but not completely prevent it. Metallic coatings with the material silver are used for VIS / IR mirrors, which are used in metrology and astronomy. In addition, silver coatings are used in the manufacture of laser mirrors (low power applications).
Wavelength | Angle of incidence | Reflection |
|---|---|---|
450 nm | 8° r-pole | 63,0 % ±1,0 % |
632 nm | 8° r-pole | 97,5 % ±1,0 % |
1064 nm | 8° r-pole | 98,0 % ±1,0 % |
Here you can find our overview to optical coatings.
Aluminum coatings can be easily vapor deposited and show uniform reflection in the visible range. Aluminum is therefore a frequently used material for optical mirror coatings. Over time, the reflection of aluminum drops due to the formation of oxide layers on the surface.
Wavelength | Angle of incidence | Reflection |
|---|---|---|
400 nm | 8° r-pole | 80,0 % ±1,0 % |
550 nm | 8° r-pole | 90,0 % ±1,0 % |
750 nm | 8° r-pole | 80,0 % ±1,0 % |
Rhodium is a high-melting precious metal, this is very hard and also chemically stable. Rhodium mirrors are therefore often used in dentistry.
Platinum is also used when a highly stable mirror surface is required. It does not oxidize and is not attacked by aggressive gases or liquids.
However, the reflectivity of rhodium, platinum and chromium is lower than that of metallic coatings such as gold, silver or aluminum. Due to their stability, they are nevertheless an alternative for use under extreme conditions.
Copper coatings are very sensitive to oxidation and should therefore always be protected with an oxide.
Nickel coatings form a good barrier layer to prevent diffusion between two metals. It is not used as an optical coating.
We can offer coatings of other metals on request. Please feel free to contact us.
Here you can find our overview of optical mirrors
High-performance functional glasses are produced by coating glass. Glass is an excellent substrate material for optical coatings because it is characterized by high thermal and chemical resistance, transparency and high mechanical stability. In the field of metallic coatings, we offer individual solutions for a wide range of demanding applications.
Take advantage of our expert advice and benefit from our custom manufacturing service. We offer a high-performance coating service on metals, semiconductors as well as all common optical glasses. Coatings made of metals are often sufficient for broadband optical applications because of their good reflection. We also develop custom coatings for laser applications and systems.
Would you like to learn more about our services? Please feel free to contact us. We will help you with your request.
