The split ratio of light transmittance and reflectance is 1:1 and is called a half mirror. Good fit for large beam size applications at a reasonable price. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding widespread application in fibre optic telecommunications. In its. An Optical Beamsplitter is an optic or optical device that is used to split a beam of light in two. Newport offers a wide variety of Beamsplitters in various shapes. a laser beam) into two (or sometimes more) beams, which may or may not have the same optical power (radiant flux).