Reflective Surfaces for Multi-Spectral, High-Thermal Stability Mirrors in Critical Applications
When compared to other metals used in mirror coating, such as diamond-turned aluminum alloys and polished nickel surfaces, AlumiPlate’s electroplated aluminum is a superior coating solution for critical optical mirror applications requiring light weight, low scatter and thermally stable performance with excellent surface finish. Electroplated aluminum is immediately beneficial for various infrared (IR), visible spectrum and multi-spectral optical coating applications and are in use by leading aerospace, defense and scientific innovators, like Raytheon Co.
Electroplated aluminum is a deterministic nickel plating alternative that can be diamond machined to a surface as smooth as 13 Angstroms (Å) rms without the need for post-machining polishing. An electroplated aluminum coated surface is ready for use directly after the diamond-turning process, and the resulting geometry offers better optical finishes and more predictable processing results than other mirror substrate materials.
Contact our technical team to learn more about aluminum mirror coatings or to discuss your specific application.
Why Choose Electroplated Aluminum for Your Optics Applications?
Benefits of Electroplated High-Purity Aluminum
Reduced Figure Distortion
Metal mirrors with diamond-turned electroplated aluminum are not susceptible to CTE mismatch or bi-metallic bending over a broad range of operating temperatures – including cryogenic. The coating is stable, soft, ductile, and free of internal stresses that could cause warping.
Improves Roughness and Scatter
NASA testing has found that a diamond-turned, high-purity, electroplated aluminum layer offers significant advantages over other alternatives in the aerospace environment. The roughness of a diamond-turned, electroplated aluminum surface ranged from 15-30 Ǻ rms – significantly better than diamond-turned 6061’s range of 30-70 Ǻ rms. Electroplated aluminum also provided nearly an order of magnitude lower scatter for a wide range of angles.
Enable Use of High-Performance Exotic Optical Substrates
Electroplated high-purity aluminum offers an optical performance and weight advantage over nickel coatings on exotic substrates such as beryllium and composites. Space-borne, spinning, or scanning mirror designs benefit from the use of these lighter, stiffer, and more thermally stable substrates, the advantages of which are negated by using a heavy nickel layer.
Allows Application of an Anodized Black Finish to any Substrate
Electroplated high-purity aluminum allows for anodizing any optical substrate with an optically flat, non-outgassing, absorptive, uniform black coating for applications requiring maximum absorption of stray radiation.
A New Standard for High-Performance Optical Reflective Surfaces
II-VI Incorporated, a pioneer and leading supplier of high end engineered optics products, has achieved an outstanding 18 Å rms diamond turned surface finish on a 2 inch diameter 6061-T6 spherical mirror plated with 0.005″ (5 mils) of high purity aluminum. II-VI also diamond turned 36 Å rms surface finishes onto an aluminum plated 3 inch diameter, 5 inch off-axis parabolic mirror.
Precitech, a premier diamond machine tool manufacturer, achieved a 20 Å rms diamond turned
surface finish on a 3″ diameter convex spherical mirror and a 13 Å rms finish on 2″ plano witness samples.
The technology for electroplating aluminum is well-established and commercially available. The coating has been specified for multiple optical programs, including all Raytheon Global Hawk Program metal mirrors.
Aluminum electroplated optics have been in service for over 20 years in a variety of scientific and defense applications. Multiple sources for diamond machining are available. Contact us for more information or to discuss your application in more detail.