A beam splitter is an optical device that divides a beam of light into two separate beams. It works based on the principle of reflection and transmission, allowing part of the light to pass through while reflecting the rest. a laser beam) into two (or sometimes more) beams, which may or may not have the same optical power (radiant flux). This ability to manipulate light makes beam splitters essential in various. Field 1 evolves as E1 ! T E3 + RE4, where T; R are the transmission and re ection coe cients for the beam splitter. Note that jT j2 is the transmitted intensity.