Uses of aluminium mirrors
Aluminium and aluminium alloys can easily replace most glass mirrors, and are popular for making lightweight scanning mirrors and galvo mirrors or where overall weight is an issue such as in aerospace, defence and medical optical systems. Customers working to optimise SWaP (size, weight and power) should be aware of aluminium mirrors.
Aluminium based mirrors are a good alternative to Silicon mirrors in moving mirror or flying optics applications as aluminium is far easier to engineer into complex shapes. Further weight saving is possible by using ribbed and pocketed designs on the rear of the mirrors.
Benefits of aluminium mirrors
Our aluminium mirrors are chemically polished. This ensures that the surfaces are super smooth and free of turning lines, fly cutting arcs and diffractive patterns that can lower the surface quality.
Our proprietary stress relieving and heat treatment gives long term stability and performance across a wide range of temperatures.
LBP Optics can make mirrors from intricately engineered parts where one face is needed to be a laser grade mirror surface. We can make flat, spherical and aspheric aluminium optics, with various mirror coatings.
Care needs to be taken to avoid galvanic corrosion when using metal optics. In the presence of moisture or water cooling dissimilar metals will cause electrochemical decomposition. Our Electroless Nickel plating can reduce this problem.
Because aluminium surfaces react with the atmosphere and lose reflectivity, most, but not all our aluminium mirrors are used with a thin film optical coating to improve reflectance and durability.
LBP Optics offer several coatings:
- Electroplated gold, for near and far infrared use.
- MaxR for 10.6um, high reflectivity for CO2 lasers.
- Protected silver for visible and near infrared use.
- A simple MgF2 overcoat for UV and visible use.
It is possible to have a thin film vacuum deposited coating optimised for other specific wavelengths, or several multiple wavelengths. For example, coatings optimised for “telecoms” wavelengths, 1 micron fiber lasers or for IR illumination.
To improve the laser damage resistance and reduce scatter, our aluminium mirrors have an intermediate layer of electroless nickel deposited. This gives an amorphous, non-crystalline surface of exceptional smoothness. Electroless nickel also protects the whole of the mirror from oxidation.