In its most common form, a cube, a beam splitter is made from two triangular glass which are glued together at their base using polyester,, or urethane-based adhesives. (Before these synthetic, natural ones were used, e.g.) The thickness of the resin layer is adjusted such that (for a certain ) half of the light incident through one "port" (i.e., face of the cube) is and th.
[pdf] For beam splitters with two incoming beams, using a classical, lossless beam splitter with Ea and Eb each incident at one of the inputs, the two output fields Ec and Ed are linearly related to the inputs through where the 2×2 element is the beam-splitter transfer matrix and r and t are the and along a particular path through the beam splitter, that path being indicated by the subsc.
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