An incident beam on a beam splitter is partially reflected and partially transmitted, and thus split into two beams. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding widespread application in fibre optic telecommunications. a laser beam) into two (or sometimes more) beams, which may or may not have the same optical power (radiant flux). Beamsplitters are often classified according to their construction: cube or plate. A lossless device implies that the transformation matrix B is unitary, which means that B 1B = ByB = 1 1 ) B = By. Recall that the matrix elements of By i;j = Bj;i. This division allows for the simultaneous analysis or utilization of the light's properties along two separate paths.