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Beam splitters

An optical element which divides the beam in to two different beam in different directions is a beam splitter. Configuration wise they are broadly divided into two types as cube beam splitter and plate beam splitters.

Applications

Laser energy splitting
Laser range finders
Night vision binoculars
Optical systems
Imaging applications
Cameras
Sensors
Projection systems
LCD displays

A beam splitter is the crucial part of most interferometers.In its most common form, a cube, it is made from two triangular glass prisms which are glued together at their base using polyester, epoxy, or urethane-based adhesives. The thickness of the resin layer is adjusted such that half of the light incident through one port is reflected and the other half is transmitted due to frustrated total internal reflection.

Another design is the use of a half-silvered mirror. This is a plate of glass with a thin coating of aluminium with the thickness of the aluminium coating such that part, typically half, of light incident at a 45-degree angle is transmitted, and the remainder reflected. Instead of a metallic coating, a dielectric optical coating may be used. Such mirrors are commonly used as output couplers in laser construction. A half-silvered mirror used in photography is often called a pellicle mirror. Depending on the coating that is being used, reflection/transmission ratios may differ in function of the wavelength.

A third version of the beam splitter is a dichroic mirrored prism assembly which uses dichroic optical coatings to divide an incoming light beam into a number of spectrally distinct output beams. Such a device was used in multi-tube color television cameras, in the three-film Technicolormovie cameras as well as modern, three-CCD cameras. It is also used in the 3 LCD projectors to separate colors and in ellipsoidal reflector spotlights to eliminate heat radiation.

PLATE BEAM SPLITTERS

Plate beam splitters are polished flat and coated glass substrates which are in general used at 45 degree in an optical system. Highly polished surface is coated with the beam splitter coating, while the other commercially polished side is coated with the broadband anti-reflection coating to minimize the spurious reflection from the other surface.

Visible & NIR Beam Splitter : Size : 10 to 50mm ; Wavelength range : 400 - 1100nm; R/T Ration : 990-10,80-20,70-30; 60-40,50-50,40-60, 30-70,20-80,10-90

DICHROIC PLATE BEAM SPLITTERS

Nd: YAG laser can have second and third harmonics. These three harmonics are useful in scientific community. When an optical system uses these harmonics, they need to combine/separate at the detector plane. A dichroic beamsplitter coating can be used to serve the purpose.

Beam Splitters & Beam Combiners : Size : 10 to 50mm ; Wavelength range : 400 - 1100nm; Cut on wavelength : 400 - 1100nm

POLARISING CUBE BEAM SPLITTERS

A cube polarizer consists of a pair of cemented precision right-angle prisms to form a cube with low output beam distortion. The hypotenuse of one of the prisms is coated with a multilayer dielectric polarizing beamsplitter coating optimized for a specified wavelength range. The four outer faces are antireflection coated with a multilayer dielectric coating to minimize surface reflection losses. An unpolarized beam is split into two orthogonal, linearly polarized components. P-polarized light is transmitted, while s-polarized light is reflected, both with negligible absorption. The extinction ratio is better than 500:1 and is used as a broadband polarizer in a standard cube configuration.

Cube beam Combiners : Size : 10 to 50mm ; Wavelength range : 400 - 1100nm; Cut on wavelength : 400 - 1100nm

DICHROIC BEAM SPLITTERS

Dichroic coatings will transmit some part of the spectrum while reflecting the other part. In a cube beam splitter it is hard to achieve the non-polarization condition especially when the angle of incidence is steeper. This beam splitter coating will transmit the visible spectrum except the specified color (Red or Blue or green). All the other four sides of the cube beam splitter are coated with broadband antireflection coating.

Cube beam Combiners : Size : 10 to 50mm ; Wavelength range : 400 - 1100nm; Cut on wavelength : 400 - 1100nm

POLKA DOT BEAM SPLITTERS

Polka dot beam splitter is vacuum deposited aluminium coating with protective dielectric layer on ultraviolet grade fused silica substrate. Coating is deposited in the circular/square type patterns of preferred dimension and spacing depending on the input beam size. When this beam splitter is placed in the input beam path, it divides the beam energy into equal halves in transmission and reflection. This coating bears the advantage of being insensitive to the angle of incidence and color neutral.