Large Area Coater Up and Running
Materion’s state-of-the-art Large Optics Coating Facility in Westford, MA is now up and running. The completion of this 18 month project significantly enhances our capability to manufacture and test extremely large optical interference filters and other complex optical coatings. The centerpiece is our large vacuum coating chamber which can coat large optics up to 1.4 meters (55 inch) diameter. While other firms may be able to coat optics this size and larger, we add greater value by producing highly complex coatings with exquisitely good uniformity over a large area. Essentially, we scale the same process used for an eight inch part to produce similar quality results for larger parts.
The coating facility includes not only the vacuum chamber, but a precision wash station to clean large optical substrates, spectral measurement instruments, and special handling equipment all housed in a clean room with measured particle counts placing it at ISO 4 (class 1000) or better. All equipment has been custom-designed for this application and has the capability to allow safe handling of large and expensive optics, with precise deposition and testing of complex interference filters consisting of a few to well over 100 layers on substrates as large as 1.4 meters diameter.
Product-wise, Materion is targeting high performance bandpass filters up to 750 mm diameter which can easily require well over 100 thin film layers of precise thickness. We are uniquely positioned to produce these filters in much larger sizes than are currently available. Additional product capabilities include beam splitters up to a meter in size, with layer counts in the 50 to 80 range, as well as enhanced mirrors up to 1.4 meters.
The coating chamber was installed in late December and after a complete check-out, development work was started. The first challenge was a 600 mm diameter narrow bandpass filter for the Subaru telescope in Hawaii. Over a few weeks in February and early March we deposited the required filter design several times on small samples to calibrate the process. The first full size substrate was coated on March 18, after which we loaded and coated the real Subaru optic, on March 21. We achieved success on the first attempt on a very exacting project!
Uniformity over the 600 mm / 24 inch diameter was held to +/- 0.2% (about +/- 1 nm in wavelength). This exceeded the requirement by about a factor of two. To put the 0.2% range in perspective, this is a physical thickness variation of 9 nm. A nm (1/1,000,000,000 meter) is the size of 3 to 10 atoms - depending upon the element. (For comparison, a virus is about 30 to 50 nm.) To summarize, this is a thickness variation of about 50 atoms across 24 inches. Accomplishing this task was a challenge but Materion staff is confident we can beat this number!
The enhanced Large Optics Coating Facility will allow Materion to meet our astronomical community customer’s requirements for larger-sized optics and support very high performance space programs, worldwide observatories and space hardware contractors. Upcoming projects include coating for additional Subaru filters as well as other large optics for a number of Observatories. Look for updates in future issues of this newsletter.
For information on Materion’s large optics coating capabilities, please contact: Thomas.Mooney@Materion.com