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What are Beamsplitters?
Edmund Optics Inc.

What are Beamsplitters?

Beamsplitter Construction | Types of Beamsplitters

Beamsplitters are optical components used to split incident light at a designated ratio into two separate beams. Additionally, beamsplitters can be used in reverse to combine two different beams into a single one. Beamsplitters are often classified according to their construction: cube or plate (Table 1).

Table 1: Comparison of Cube and Plate Beamsplitters
Cube BeamsplittersPlate Beamsplitters
Cube Beamsplitter
Figure 1: Cube Beamsplitter
Plate Beamsplitter
Figure 2: Plate Beamsplitter

Cube beamsplitters are constructed using two typically right angle prisms (Figure 1). The hypotenuse surface of one prism is coated, and the two prisms are cemented together so that they form a cubic shape. To avoid damaging the cement, it is recommended that the light be transmitted into the coated prism, which often features a reference mark on the ground surface.

Plate beamsplitters consist of a thin, flat glass plate that has been coated on the first surface of the substrate (Figure 2). Most plate beamsplitters feature an anti-reflection coating on the second surface to remove unwanted Fresnel reflections. Plate beamsplitters are often designed for a 45° AOI. For substrates with a 1.5 index of refraction and a 45° AOI, beam shift distance (d) can be approximated using the equation in Figure 2.

Table 2: Beamsplitter Construction
Cube Beamsplitters
  • Easy Integration with 0° AOI
  • No Beam Shift
  • Equal Reflected and Transmitted Optical Path Lengths
  • Shorten the Optical Path of a System
  • Heavy, Solid Glass Construction
  • Difficult, and more Expensive to Make in Large Sizes
Plate Beamsplitters
  • Lightweight
  • Relatively Inexpensive
  • Easy to Manufacture in Larger Sizes
  • Reflected and Transmitted Optical Paths are Different Lengths
  • Beam Shift of Transmitted Light (see Figure 2)
  • The 45° AOI may Require Additional Alignment Time
Cube Beamsplitter Setup

Types of Beamsplitters

Standard Beamsplitters are commonly used with unpolarized light sources, such as natural or polychromatic, in applications where polarization state is not important. They are designed to split unpolarized light at a specific Reflection/Transmission (R/T) ratio with unspecified polarization tendencies.

Polarizing beamsplitters are designed to split light into reflected S-polarized and transmitted P-polarized beams. They can be used to split unpolarized light at a 50/50 ratio, or for polarization separation applications such as optical isolation (Figure 3).

Polarizing Beamsplitter
Figure 3: Polarizing Beamsplitter

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. These beamsplitters are ideal for maintaining polarization in applications utilizing polarized light (Figure 4).

Non-Polarizing Beamsplitter
Figure 4: Non-Polarizing Beamsplitter

Dichroic Beamsplitters split light by wavelength. Options range from laser beam combiners designed for specific laser wavelengths to broadband hot and cold mirrors for splitting visible and infrared light. This type of beamsplitter is commonly used in fluorescence applications.

Browse our selection of plate, cube, polarizing, non-polarizing, pellicle, or polka dot beamsplitters in a variety of R/T ratios or substrates.

Edmund Optics offers plate, cube, pellicle, and polka-dot beamsplitters. Interested in learning about benefits and differences?

Beamsplitters do exactly what their name implies: split incident light beams. Learn about the benefits and types of beamsplitters to see which is best for you.

To understand how the most popular prisms work and how each can best be used in light reflection and refraction applications, read this easy-to-follow application note.

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