Highly reflective layers: dielectric mirrors
The use of dielectric and thus virtually non-absorptive layers enables mirrors to be produced with reflections up to greater than 99 %. In addition dielectrically-coated mirrors are characterized by greater hardness and good resistance to chemical action.
Properties of metal mirrors with a highly reflective coating
Metal mirrors are manufactured in a high vacuum; during this process, a highly reflective material such as aluminium, silver or gold is vapour-deposited onto a substrate material. Generally plane or curved optical materials have metal coatings vapour-deposited on them. The reflectivity of the resulting mirror depends on the metal used.Aluminium is one of the standard coatings for a metal mirror for wavelengths ranging from visible light to the IR range. To prevent damage, the metal mirrors are coated with a protective layer of SiO2. The optical properties of metal mirrors are constant across a wide spectral range. They are only marginally dependent on the angle of incidence and have only a limited polarizing effect. However, their spheres of application are limited by their significant levels of absorption, reduced hardness compared to dielectric layers and susceptibility to chemical action.
Measuring reflection values in metal mirrors
It only makes sense to measure reflection at extremely high reflection values and under various angles of incidence of 0 - 60° using absolute measurement (the “VW” measuring principle). These reflection measurements were conducted with URA on our in-house Lambda 950. For spectroscopy, the wavelengths are converted into the wavelengths of light applicable to the vacuum.
Our dielectric and metal mirror layers are suitable for a wide variety of substrates. Among other things, we can coat
- plastic, for example COP (Zeonex among others), COC (from TOPAS) or PC
Other materials can also be coated, however - we would be pleased to advise.
Product benefits for you
We give a high priority to customer-specific and individual coating solutions for different substrate sizes, shapes and materials. For HR coatings/metal mirrors, both our modern system technology and the relevant properties of the mirror layers provide you with significant benefits:
- the option of coating large substrates (up to 1200 mm long)
- broad wavelength range
- constant across a broad spectral range
- thermal resistance of coating
- good heat conductivity
- corrosion resistance
Spheres of application for products with HR coatings
Spheres of application for dielectric metal mirrors can be found not only in a large number of different laser applications, but also in numerous other areas.Functional surface coatings serve among other things to increase reflection, control polarization or simply to protect from mechanical damage.Metal mirrors, especially for use with CO2 lasers, are applied in a ion-assisted vacuum vapour-deposition process and compared to conventional vacuum layers, have better hardness values and consequently good resistance to cleaning.
As a purely metal layer, it can also be used across a large wavelength range, for NdYAG lasers as well as for CO2 lasers.
- Metrology, e.g. laser mirrors for adjusting laser beams
- Optical systems with laser resonators
- Medical technology - diagnostics, for example
- Dental mirrors
- Astronomy mirrors
- and many others