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Rugged Rugate Filters

Rugate FiltersRugate offers an extremely versatile technique for the construction of optical rejection filters.  They are particularly well suited to optical applications in which narrow bands of light are to be removed from a broad spectral band.

Materion’s Role in Rugate Technology

Rugate Filter Technology was developed several years ago at Materion’s Westford, MA location through a series of US Air Force development programs. These programs allowed us to create a robust cost-effective means for producing filters with deep rejection bands but very wide windows of transmission.  This valuable capability can be readily employed in multiple applications for which narrow spectral bands are redirected from a broad spectral range.

Fabrication of Rugate Filters

Materion fabricates Rugates from a wide range of materials depending on the spectral requirements of the filter. The vast majority are manufactured with refractory metal oxides for use in the visible and short wave infrared.  Rugates are fabricated by combining two or more materials to form a continuously varying composition as a single layer solution.  As a single layer, they have no internal interfaces.

In a Rugate filter, the number of bands, their spectral location, band width and level of rejection are all independently controllable.  Although independent these parameters combine to define the complexity of the structure, its thickness hence its yield and cost.  Features such as longer wavelength, higher rejection, narrower width and steep slopes - all increase the thickness of the coating and hence its cost.  Materion designers will work with you to obtain the solution that best meets your needs by trading the various cost performance alternatives.

Figure Caption:  Three-band Rugate with notches in the Visible, SWIR and MWIR spanning the transmission window of the Al2O3 substrate illustrating the broad applicability of this technology for multi and hyper-spectral imaging systems.

Rugate Filter Chart

Available Rugate Filters

Materion has designed and fabricated Rugates with as many as 43 notches, although typical designs have one to three rejection zones. We have made Rugates:

  • Up to 24 inches in diameter, but our typical diameters are less than 12 inches
  • With notches from below 300 nm to beyond 10000 nm
  • In quantities from one to hundreds of thousands units

More on Materion Rugate filters…

As an innovator of high quality filters, Materion has the unmatched heritage and engineering expertise to provide long-range solutions. Our Rugates are particularly rugged: we have had filters in 95% RH/65o for well over a decade with no measurable degradation in performance.  For more information about how we can meet your challenging filter requirements, contact Robert Sprague, Director of Technology,