Optical Beam Splitters consist of an optic coated with a multi-layer dielectric film that splits the incoming energy into reflected and transmitted components in a defined way over a given wavelength region. Over wide wavelength regions, all beam splitters are polarizing to some extent, although plate beam splitters are less polarizing than cube beam splitters.
NTFL can design and deposit custom beam splitter coatings to customer specifications. If you are not sure how to specify your coating, our coating engineers will work with you to identify the best design for your needs.
Beam Splitters are useful in interferometry, fiber optics, metrology, oceanography, seismology, chemistry, plasma physics, remote sensing, biomolecular interactions, surface profiling, micro fluidics, mechanical stress/strain measurement, and velocimetry.
Plate Beam Splitters (PBS) are constructed of flat glass with a dielectric multi-layer beam splitter coating on one surface and an anti-reflection coating on the second surface. Beam splitters can be designed for a wide range of angles, but are typically used at 45 °. The dielectric coating used to construct plate beam splitters have low absorption coefficients, so to a very good approximation, R + T = 1. The result is that the transmittance equals the difference between 100% and the percent reflectance.
This graph features reflectance curves for various 45 ° plate beam splitters for random polarization (second surface anti-reflection coated)
Cube Beam Splitters (CBS) are typically constructed from two right angle prisms that are cemented together with an index-matched adhesive hypotenuse-to-hypotenuse with a dielectric coating in between.
For most applications, the prism legs are anti-reflection coated. Cube beam splitters operate by passing one polarization and reflecting the other over a relatively narrow wavelength region. So for randomly polarized light (50% p-polarized and 50% s—polarized), the cube beam splitter passes one polarization and reflects the other, resulting in a polarizing 50/50 beam splitter.
For this reason, cube beam splitters are also employed as polarizers.
Unpolarized light incident upon the entrance face of the cube at normal incidence is internally incident at 45 degrees upon the multi-layer coating. The coating serves to separate energy into two polarized beams. The beam transmitted through the cube is linearly polarized to a purity of 98% or better, with the plane of the electric field vector parallel to the plane of incidence (p-polarized). The beam which exits the cube at a right angle to the incident beam (reflected by the coating) is linearly polarized to a purity of 98% or better with the electric field vector orthogonal to the plane of incidence (s-polarized). Beam splitting cubes can be designed for most wavelength region.
This graph features transmittance for a right angle cube beam splitter. The blue curve is for p-polarized light, the red curve is for s-polarized light and the purple curve is for randomly polarized light.
NTFL manufactures many types of plate beam splitters and cube beam splitters. Contact us with your specific requirements. If you would like more specific information concerning plate beam splitters (PBS) or cube beam splitters (CBS), please contact us.
** (Available in the ultraviolet, visible and infrared)