Optical Beam Splitters

Optical components used to split incidental light at a designated ration into two distinct beams are known as beamsplitters. Beamsplitters can also be used to do the opposite. By reversing the orientation the beamsplitter will combine two separate beams back into a single one. There are two different styles of beamsplitter construction: plates and cubes.

Constructing a cube beamsplitter consists of combining two right angle prisms. The longest side of one of the right angle prisms (hypotenuse) is coated, and the two are cemented together to form a cube. Light should be transmitted into the coated side of the prism, identified by a reference mark on the ground surface, to avoid damaging the cement during use.

Plate beamsplitters are made up of a thin, flat piece of glass that has been coated on the first surface of the substrate. Most plate beamsplitters also have an anti-reflection coating on the second surface to avoid any Fresnel reflections during use.

When light needs to be split into reflected S-polarized and P-polarized beams, a polarizing beamsplitter can be used. Polarized beamsplitters split unpolarized light at a 50/50 ratio, and can also be utilized for polarization separation when in optical isolation applications.

Ideal for maintaining polarization in applications utilizing polarized light, non-polarizing beamsplitters split light into a specific R/T ratio while maintaining the incident light’s original polarization state. For example, in the case of a 50/50 non-polarizing beamsplitter, the transmitted P and S polarization states and the reflected P and S polarization states are split at the design ratio.

Commonly used in fluorescence applications, Dichroic Beamsplitters split light by wavelength and provide a variety of options in applications such as laser beam combiners designed for specific laser wavelengths or broadband hot and cold mirrors used for splitting visible and infrared light.