a system that divides a beam of light, electrons, etc, into two or more paths
beam splitter in American English
noun
an optical device with a special mirror or prism system that separates a beam of light into component beams, used in making holograms, separating colors in a color TV camera, etc.
: occasionally written ˈbeamˌsplitter (ˈbɛmˌsplɪtər)noun