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A beam splitter (or beamsplitter) is an optical component used for splitting light into two separate beams, usually by wavelength or polarity. It can also be used, in reverse, as a beam combiner, to join two light beams into one. These specialty mirrors have applications in many fields, including laser, semiconductor and phototonics instrumentation.

Shanghai Optics manufactures a wide variety of high quality beamsplitters optimized for different applications. We also offer both plate and cube design options.  Our options include polarizing beamsplitters, non-polarizing beamsplitters and dichroic beamsplitters. Shanghai Optics also offers a wide range of custom optical beam splitters.  All our beamsplitters are made of high quality glass, with high surface quality to allow tight tolerance on all parameters.

Beamsplitter Designs

Cube Beamsplitter

Cubic beamsplitters usually consist of two right angle prisms that are carefully cemented together with optical glue. The thickness of the optical glue depends on the wavelength of light in the intended application. One inner surface of one of the prisms are coated with a partially reflective metal di-electric coating.

The cube should always be oriented so that incident light enters the coated prism, in order that energy passing through the optical cement is minimized. Entering through the wrong side will cause more than triple the amount of energy to pass through the delicate cement layer. If used in this way with high power light sources, the cement may degrade over time. We place a reference mark on the ground side of the coated prism to make it easy to orient your cube correctly.

These cube beam splitters have no beam shift and can be easily integrated with 0 degree angle of incidence. The reflected and transmitted optical path lengths will be equal. Compared to other options, they allow you to shorten the optical path of a system. Their only disadvantages are the heavy construction—each piece is solid glass – and the fact that they are both difficult and expensive to make in large sizes. We recommend these beamsplitters in situations where a simplified mounting is important and durability is premium.

Cube beamsplitter diagram:

Plate Beamsplitter

Plate beamsplitters, on the other hand, are lighter and less expensive, and they can be easily manufactured in any size. They consist of a flat, thin glass plate, with a coating on the first surface of the substrate. It is this coating which splits the incident beam by a specified ratio.  The reflected and transmitted optical paths will have different lengths, and there will be a beam shift in transmitted light. Although these optics are often designed for a 45 degree angle of incidence, setup may require extra alignment time. Plate beam splitters are cheaper to manufacture than are cube beamsplitters.

Plate beamsplitter diagram:

 

beamsplitter glass

Types of Beamsplitters

Dichroic Beamsplitters

A dichroic beamsplitter is an optical filter, or dichroic mirror, which transmits selected wavelengths while reflecting others. These beam splitters are typically used at non normal angles of incidence. If the dichroic beamsplitter is placed at an orientation of 45 degrees to the incident light, the reflected light will make an angle of 90.

Dichroic beamsplitters are nonabsorbent, so all light is either transmitted or reflected.

When selecting the ideal dichroic beam splitter for your application, you will want to consider:

  • Transmission range—the wavelength range for which the optic transmits
  • Reflection range—the wavelength range for which the optic reflects
  • Polarization— a measure of the degree of beam separation due to polarization

Edge steepness is defined as the slope of the edge, or cut off point, between reflection and transmission. A steep edge refers to a sharp transition between the reflected zone and transmitted zone. The cut-off edge, abbreviated SP, is defined as the wavelength of the edge at 50% of the maximum transmission of the filter, halfway between full transmission and full reflectivity.

Our dichroic beamsplitters feature very steep edges, and our narrow spectral band edge tolerances ensure you will have the maximum possible spectral stability.

Polarizing Beamsplitters

As its name suggests, these optics divide a light beam into two separate beams, splitting light according to its polarity. They are often used to transmit p-polarized light while reflecting all s-polarized light in a different direction. The polarizing beamsplitters we manufacture at our factory include cubic beamsplitters, plate beamsplitters, and lateral displacement beamsplitters.

Non-polarizing Beamsplitters

A non-polarizing beam splitter is used to split light independently of polarization state. These filters have very small polarity dependences (typically about 3-6%). Our non polarizing beam splitters have applications in laser beam manipulation and interferometry, and we offer both plate and cubic options. These dichroic mirrors can be customized with a metallic coating offering partial reflection for the wavelength of your choice.

Other Types of Beamsplitters

Lateral Displacement Beamsplitters

If an incident beam should be divided into two displaced parallel beams, you will want to use a lateral displacement beamsplitter. Our precision lateral displacement beamsplitters, which consist of a rhomboid prism cemented to a right angle prism, ensure that exiting beams have no more than 30 arcsec deviation from parallel. A multi layer anti reflection coating on both entrance and exit faces can provide increased efficiency.

Laser Beamsplitters

Laser beamsplitters separate a laser beam into two sectors, and are usually meant to reflect part of a beam (either differentiated by wavelength or polarization). For laser applications cubic, plate, or lateral displacement beamsplitters are all possible options, and each of these can be custom-made for laser wavelengths. Surface quality is essential for any laser optics, and our state of the art machinery and careful quality control ensures that every optic to leave our factory meets all applicable standards.

Custom Options

Please contact us to discuss beam splitter designs or a custom order. Our team is experienced in optical design, and we can help you determine the ideal beamsplitter for your situation, and aid you as you progress from blueprint to prototype to full scale production of your optical product. We are able to produce custom beamsplitters tailored to your specific wavelength ranges needs and tolerance levels.

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