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Unknown to most people, beamsplitters play a major role in the gadgets we use and encounter every day. They are the unsung technology behind the awesome devices we enjoy today. Interested in knowing more about this wondrous device? Then read on.

In this article, we will answer these questions: what is a beam splitter, what are the common types of beam splitters, and how does a beam splitter work in various devices.

What Is a Beamsplitter

A beamsplitter (or beam splitter) is an optical device that splits an incident light into two separate beams traveling in different directions. Typically made of glass, a beam splitter divides the light passing through it at a ratio. Usually, half of the light is reflected at an angle, and the other half is transmitted to the opposite side of the light source. A beamsplitter can also work in reverse, capturing two light sources and then combining them into a single beam of light.

Beam splitter types are distinguished according to their construction and properties. We will dive further into the different kinds of beamsplitters and where they are used. The versatile quality of beam splitters makes them indispensable in various industries worldwide.

Major Examples of the Usefulness of Beam Splitters

There are numerous applications of beam splitters in our world today. Various scientific fields and industries make use of this highly versatile technology. Smart mirrors, cameras, and lasers, all these devices use a beam splitter. In addition to that, we have listed down the most common instruments that employ a beam splitter.

  • Dielectric
    Digital signage, Mirror TVs, Fluorescence microscopy
  • Smart mirror
    Smart mirrors, Virtual reality (VR) glasses, Hidden security cameras
  • Teleprompter
    Teleprompting screens, Holograms, Illusions, and Special effects
  • Two-way glass
    Infinity mirrors, Home privacy, Mirrors in reality TV sets
  • Optics
    Fiber optic and broadband internet, Microscopes, Binoculars, Cameras, Projectors, Augmented reality glasses, and Smart glasses
  • Lasers
    Laser cutting, Aesthetic laser treatments, Laser speed gun, Distance measuring instrument

Common Types of Beam Splitters

Beam splitters are categorized based on their properties. For example, cube vs plate, polarized vs non-polarized, and dielectric vs mirror. Let us further discuss these categories in detail and their applications.

A Cube Beam Splitter

One of the most common categories is the cube beam splitter. It is composed of two triangular right-angle prisms cemented together at the hypotenuse to form a cube. The thickness of the optical glue used to bind the two glasses together is determined by the beam splitter’s purpose.

One of the prism’s inner surfaces is coated with a dielectric film that reflects at a 90° angle the half of the incident light that passes through. The other half is transmitted at 0° straight to the other side, meaning there is no beam shift and thus shortening the optical path of a system. Both the reflected and the transmitted beams are of the same length.

One of the disadvantages of this system is its construction and cost. The components are made of solid blocks of glass, which are both heavy and expensive to produce. On the other hand, its solid structure ensures a more durable device that only requires a simple mounting system.

A Plate Beam Splitter

Another common category is the plate beam splitter. It is a thin, flat glass with a coating on one side facing the incident beam. The coating will determine the ratio at which the incident beam of light is divided. These are usually used for a 45° setup but may need some time to adjust. Unlike a cube beam splitter, a plate beam splitter will produce different lengths of the reflected and the transmitted beams.

The advantages of plate beam splitters are their low production cost and their lighter construction. These are thin pieces of glass that are less expensive and also lighter in comparison to cube beam splitters. However, as it is thin and more fragile than a cube, it will require a more secure and substantial mounting system.

What Is a Dichroic Beam Splitter

A dichroic beam splitter, or dichroic mirror, works as an optical filter that selects certain wavelengths and reflects the others. These are often employed at non-normal angles of incidence. Dichroic beam splitters can only reflect or transmit light, as it is non-absorbent. It also means that there is no loss of light using this type of beam splitter.

These are some considerations you should think of when choosing a dichroic mirror for your applications:

  1. Transmission range—the range of wavelengths at which the optic transmits light
  2. Reflection range—the range of wavelengths at which the optic reflects light
  3. Polarization— the angle of beam separation caused by the process of polarization

Its ability to divide the incident light into spectrally distinct beams and vice versa makes it an indispensable device in movie cameras and LCD projectors.

How Polarized Beam Splitter Works

Polarizing beam splitters divide light into two directions based on their polarity. The incident beam is split orthogonally or into two right angles, the p-polarized beam is reflected while the s-polarized light is transmitted. This is well suited for high-output power devices such as lasers.

Another popular application of polarizing films is on polarized sunglasses and vehicular mirrors. The film removes the glare, thus giving us a clear image without reflective light. This makes it safer for individuals maneuvering traffic when the sun’s rays are intense and also during night driving.

How Non-Polarized Beam Splitter Works

A non-polarized beam splitter does not care about the light’s polarity or charge. It merely separates the beam while keeping its current state of polarity. It is commonly used in interferometry and laser beam manipulation.

Other Types of Beamsplitters

Lateral Displacement Beam Splitter

A lateral displacement beam splitter splits the incident light and produces two displaced parallel light beams. It is composed of a rhomboid prism glued to the hypotenuse of a right-angle prism. Multiple layers of anti-reflective (AR) film on both the entrance and exit surfaces increase the efficiency of the optical components. Polarizing or non-polarizing coatings can be applied to fit your purposes. This beam splitter is usually utilized in separating or combining laser beams.

Transmission Grating Beam Splitter

A transmission grating beam splitter separates the incident light into its component wavelengths. Its ability to dissect and detect weak signals makes it a great optical component in fluorescence microscopy. The gratings can also be adjusted to lessen image distortion of objects in low light conditions. This makes it highly useful in creating large telescopes that can focus and deliver clear images of faraway objects in space.

Perforated or Polka-Dot Beam Splitter

A polka-dot beam splitter has an aluminum optical coating in the form of dots across the surface. These dots reflect light, while the rest of the light is transmitted through the uncoated surface. There is usually a 50/50 ratio of reflected and transmitted light in this system. Its best application is in white light illumination, such as in halogen and tungsten lamps.

Beam Splitter Coatings

Coatings or filters are placed on optical surfaces to enhance the reflection, transmission, and polarization of light. Without optical coatings, the glass components lose a percentage of light as it passes through, giving you a less efficient system.

The thin films are usually made out of oxides and metals. A combination of coatings made out of different materials and varying thicknesses is used to produce the correct ratio of reflection and refraction that is needed for your application. A high-quality coating delivers better results and protects against scratches and dirt.

These are some of the more common coatings used on optical components:

A polarizing coating separates light into beams based on their polarity. It enhances the output power of laser beams.

A dielectric coating creates an electric barrier, which reduces conductivity and the risk of electric shock. This is best used in high-voltage systems.

A metallic mirror coating ensures that there is more light reflected back, which makes the reflected image clearer.

Aside from enhancing the effects of beam splitters, these films protect the surfaces of your optical devices. This ensures the longevity of your beam splitter and its components.

In Summary

Optical beam splitters are versatile devices, typically made of glass, used in separating or combining light beams. These optical components play a major role in the science and tech industry. Most people are unaware, but almost all the glass and mirrors around us utilize beam splitters. Utilizing different types of beam splitters, we enjoy the benefits of cameras, smart mirrors, and lasers, to name a few.

If you are in need of beam splitters, Shanghai Optics is an excellent choice. We are the leading supplier of custom optics in the Photonics industry. With over 55 years of experience, we provide only the best service and high-quality components to our clients. Our facilities are ISO 9001:2015 certified, using state-of-the-art technology and processes to deliver optical products of the highest standards.


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