Beam Splitters

Common beam splitters are used to split or combine a laser beam. However, polarization beam splitters are used to split or combine two perpendicular polarization laser beam. The performance of beam splitters is mainly dependent on the coating specifications.

Beam splitter plate is a plate of glass with a thin coating of aluminum (usually deposited from aluminum vapor) with the thickness of the aluminum coating such that part, typically half, of light incident at a 45-degree angle is transmitted, and the remainder reflected. Instead of a metallic coating, a dielectric optical coating may be used. Such mirrors are commonly used as output couplers in laser construction. A half-silvered mirror used in photography is often called a pellicle mirror. Depending on the coating that is being used, reflection/transmission ratios may differ in function of the wavelength.