Wedge Prisms
Definition: prisms with a small angle between the end surfaces
Alternative term: wedges
German: Keilprismen
Author: Dr. Rüdiger Paschotta
Cite the article using its DOI: https://doi.org/10.61835/vbq
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Prisms having only a small angle (e.g. a few degrees) between the input and output surfaces are called wedge prisms. They are typically used for slightly deflecting (steering) laser beams. For a small angle <$\alpha$> between the prism surfaces, the obtained beam deflection angle is approximately <$(n - 1) \alpha$>, where <$n$> is the refractive index of the prism. For a typical glass prism, where the refractive index is around 1.5, the deflection angle is about half the prism angle.
The input and output surface are usually anti-reflection coated for the intended operation wavelengths. Such prisms are available from stock for various common laser lines and alternatively with broadband coatings.

By combining two wedge prisms to a Risley prism pair, one can realize an adjustable amount of beam deflection, depending on the relative orientation of the prisms.
Precision prisms are available where the wedge angle is very precisely defined, e.g. with a tolerance in the arcseconds range.
Wedge prisms are often made with a circular cross-section (so that they could strictly speaking not be called prisms!), suitable for insertion into a rotatable mount. Such a round prism may be placed on a rotating axis, resulting in a rotating beam direction.
Wedges may also be used for fine adjustment of the amount of material inserted into a beam, e.g. in order to adjust the obtained amount of chromatic dispersion for ultrashort pulses. If the wedge angle is sufficiently small, there is no substantially variation of path length within the beam diameter. Variable insertion also causes a slight transverse offset of the beam position.
Wedge prisms are usually not used as dispersive prisms, since the obtained angular dispersion is quite small.
Suppliers
The RP Photonics Buyer's Guide contains 28 suppliers for wedge prisms. Among them:


Knight Optical
Offering ultimate control over beam steering, our wedge prisms are available in UV (which can be manufactured from calcium fluoride or UV-grade fused silica to work efficiently at 175 nm and transmit 85% at 185 nm), visible and near-infrared (NIR) substrates. Available as custom-made components, Knight Optical's wedge prisms can meet the needs of every project.


Edmund Optics
Edmund Optics offers a variety of specialty prisms to choose from, including wedge prisms.


Shalom EO
Shalom EO offers wedge prisms with high precision which are ideal for laser beam steering. Our prisms are made of BK7, ultra-violet (UV) grade fused silica, CaF2 or ZnSe. Coating options include no coating, single wavelength AR coating, or broadband anti-reflection BBAR coatings on both surfaces. Other custom options are also available.


Artifex Engineering
Artifex offers custom wedge prisms tailored to your requirements. A wide range of substrates in custom sizes, specifications and coatings are available to suit your requirements. We look forward to your inquiry.


EKSMA OPTICS
We offer standard and precision wedge prisms made from BK7 or UV-grade fused silica with a wide range of values of diameter, thickness and wedge angle.

Ecoptik
Ecoptik can produce custom prisms, such as e.g. wedge prisms with an integrated lens. Tell us what you need, and we are happy to develop a suitable custom version.
See also: prisms
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