Beamsplitters: A Guide for Designers

Plate beamsplitters consist of a thin plate of optical crown glass with a different type of coating deposited 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 degrees. The second surface has an antireflection coating optimized for 45 degrees.

The transmittance and reflectance curves shown in Figures 1 through 6 are for unpolarized inputs at an angle of incidence of 45 degrees. As can be seen from the p- and s-polarization components of the transmitted beams, these beamsplitters are highly polarization sensitive. For clarity, only the average polarization reflectance curve has been presented.