Plate beam splitters consist of a thin plate of optical glass with a different type of thin film coating on each side. The first surface is coated with an all-dielectric film having partial reflection properties over either the visible or the near-infrared spectrum. The benefit of this type of coating is that it has low absorption, typically 0.5 percent for a 50/50 splitter at 45°.
Cube beam splitters consist of two identical right-angle prisms with their hypotenuse faces cemented together. Prior to cementing, a partial reflection film is deposited onto one of the faces. For best results, the incident beam should be on one of the faces of this prism. For better performance cube beams plitters should be antireflection-coated on all four faces to minimize ghost images.
Cube beam splitter have several advantages over plate beam splitters and are widely used for a variety of reasons. Cube beam splitter deforms much less when Compare to plate Beam splitter . Most of the unwanted reflections from a cube beam splitter are in the retro direction and do not contribute to ghost images. The coating is very resistant to degradation with time because it is concealed in between prisms of the cube.