Common types of beam splitter are either cube beam splitters or plate beam splitters (such as mirrors), as described below. Cube beam splitters are made from two triangular glass prisms glued together, as seen in Fig.2A-C. The thickness of the glue is carefully adjusted so that, for certain wavelengths of light, half the light that enters the cube is reflected 90° and the other half is transmitted through the cube in the same direction as it entered, as seen in Fig.2A. http://www.jxzb-mechanical.com/splitter/