Polarizing Beamsplitters

Types of Polarizing Beamsplitters

Polarizing beamsplitter can be divided into three kinds: plate polarizing beamsplitters, cube beamsplitters, and lateral displacement beamsplitters.  All three types separate the light radiation into two beams with orthogonal polarization.  The ratio of reflected to transmitted light in a perfect beamsplitter will always be 50/50.

• Plate polarizing beamsplitters  are typically designed with special hard coatings on the front surface of an optical substrate like UV fused silica. As they have a high damage threshold, they are a good choice when high transmission, a high extinction ratio, and a high damage threshold are necessary.  A plate beamsplitter has a distinct front and back side and  is designed to be used at a 45 degree angle of incidence. Typically, a small arrow will be engraved on the beamsplitter to show the appropriate direction of light.  S-polarized will be reflected at 45 degrees, while p light will be transmitted. 
• Polarizing cube beamsplitters are formed from two prisms, one of which has a dielectric beam splitting coating on the hypotenuse side. The two prisms are placed with hypotenuse sides against each other and  bound together with optical cement.  Light may enter at any of the polished square faces of the cube, which will split light into s and p polarized beams. These polarizing beamsplitters are a great choice when you need a durable beamsplitter or would like simplified mounting and system integration.  They are typically manufactured with a broadband anti-reflection coating on all faces. For laser line cube beamsplitters, our clients may choose between AR coatings optimized for  532 nm, 633 nm, 780 nm, 980 nm, 1064 nm, or 1550 nm laser wavelengths. 
• A lateral displacement beamsplitter is formed by a rhomboid prism cemented to a λ/8 right angle prism. Both entrance and exit faces will typically be coated with high quality anti-reflection coatings as well as polarizing coatings. This type of beamsplitter is less common than cube or plate beamsplitters, but is highly desirable to simplify bench top layout.