Top: implementation of the optics assembly. It consists of an upper and a lower block, A and B, mounted in a precision bracket or “cradle”, C. Bottom: the upper piece, A, is a single aluminum block into which four mirror surfaces (M4, M4′, M5 and M5′) have been machined. The lower piece, B, is also an aluminum block where the M3 mirror was machined together with mounting structures for the grid (G), beam splitters (BS and BS′), beam dumps and mixers. For the sake of clarity, the beam dumps are not shown here.