Prisms and slabs made of high-refractive-index materials such as ZnSe, Ge, and Si can be designed as broadband, 50%-50%, beam splitters (BSs) for obliquely incident s- polarized light in the near- and mid-IR. The beam-splitting face of the prism or slab is uncoated, while the exit face is antireflection coated. The split beams travel in orthogonal directions when light is incident at the Brewster angle. A novel design is also described that uses Brewster-angle reflection at the SiO2-Si interface to achieve a 50%-50%s-polarization BS over the 1.2-3.5 μm spectral range. Such s-polarization BSs are particularly suited for interferometry and holography.
R. M. A. Azzam, "Infrared broadband 50%-50% beam splitters for s-polarized light," Appl. Opt. 45, 4572-4575 (2006)