We describe diamond-turned material tests for the integral field unit (IFU) for the FRIDA instrument (inFRared Imager
and Dissector for the Adaptive optics system of the Gran Telescopio Canarias). FRIDA is closely based on the design of
the successful FISICA cryogenic infrared image slicing device, which used "monolithic" mirror arrays, diamond turned
into single pieces of metal. FRIDA, however, will require better roughness characteristics than the 15nm RMS of
FISICA to avoid light scatter in FRIDA's shorter wavelength limit (900nm). Al 6061 seems to be limited to this
roughness level by its silicate inclusions so some new combination of materials that are compatible with FRIDA's Al
6061 structure must be found. To this end, we have tested six diamond-turned mirrors with different materials and
different platings. We used the Zygo interferometer facility at IA-UNAM to do warm and cold profile measurements of
the mirrors to investigate possible bimetallic deformation effects. We present a detailed comparison of the various
performance characteristics of the test mirrors.
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