Epitaxial single-crystal chemical-vapor-deposited diamond with (100) crystal orientation is obtained from Element Six (Ascot, United Kingdom) and Apollo Diamond (Boston, Massachusetts). Both companies supply squares with thicknesses of 0.35 to . Element Six also provides disks with a state of the art diameter of 10 to and a thickness of . The absorption coefficient measured by laser calorimetry at is for squares from Element Six and for squares from Apollo. One Apollo specimen has an absorption coefficient near those of the Element Six material. Absorption coefficients of Element Six disks are 0.008 to . Each square specimen can be rotated between orientations that produce minimum or maximum loss of polarization of a laser beam transmitted through the diamond. Minimum loss is in the range 0 to 11% and maximum loss is 8 to 27% . Element Six disks produce a loss of polarization in the range 0 to 4%, depending on the angle of rotation of the disk. Part of the 0.04 to 0.6% total integrated optical scatter in the forward hemisphere at can be attributed to surface roughness.