Progress in very lightweight optics using graphite fiber composite materials

We report progress in the fabrication of very low areal density (,5 kg/m 2 ) optical mirrors using space-flight-qualified graphite-fiber- reinforced cyanate ester composite materials. Previous attempts have been thwarted by fiber print-through at the surface. We find that the problem can be successfully overcome if the composite is processed to leave a very thin layer of resin at the surface. Results thus far include replicas with surface microroughness ,1 nm rms, midfrequency ripples ,3 nm rms, areal density 2 kg/m 2 at 42-cm aperture, and freedom from print-through after vacuum drying and ion milling. The process is being extended to the fabrication of very lightweight meter-class optics for space UV astronomy applications, x-ray optics, and other ground- and space-based applications. © 1998 Society of Photo-Optical Instrumentation Engi- neers. (S0091-3286(98)04002-1)

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