A beamsplitter is a common optical component that partially transmits and partially reflects an incident light beam, usually in unequal proportions. This. on non-absorbing beam splitters. If we neglect the three-dimensional character of the electromagnetic fields and focus on one-dimensional propagation only, we can regard a beam splitter simply as a dielectric plate, possibly consisting of several y consisting of several layers ropagation along. Optical lossless beam splitters are frequently encountered in fundamental physics experiments regarding the nature of light, including “which-way” determination of light particles, N. Bohr's complementarity principle, or the EPR paradox and all their measurement apparatus.