A beam splitter or beamsplitter is an optical device that splits a beam of light into a transmitted and a reflected beam. 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. Diagram of entangled photon generation: A pump beam induces type-I spontaneous parametric down-conversion (SPDC) in a nonlinear crystal, producing a polarization-entangled photon pair (signal and idler modes). The pair is input to a 50:50 beam splitter, 700-1100nm creating path-entangled output. Edmund Optics offers plate, cube, pellicle, polka dot, or specialty prism Beamsplitters in a variety of anti-reflection coatings or substrates.