Two-layer anti-reflection coating with mullite and polyimide foam for large-diameter cryogenic infrared filters

Understand

We have developed a novel two-layer anti-reflection (AR) coating method for large-diameter infrared (IR) filters made of alumina, for the use at cryogenic temperatures in millimeter wave measurements.

• Thermally- sprayed mullite and polyimide foam (Skybond Foam) are used as the AR material.
• An advantage of the Skybond Foam is that the index of refraction is chosen between 1.1 and 1.7 by changing the filling factor.
• Combination with mullite is suitable for wide-band millimeter wave measurements with sufficient IR cutoff capability.