Wedge Prisms

Author: the photonics expert Dr. Rüdiger Paschotta (RP)

Definition: prisms with a small angle between the end surfaces

Alternative term: wedges

Category: article belongs to category general optics general optics

DOI: 10.61835/vbq Cite the article: BibTex plain text HTML Link to this page! LinkedIn

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. 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.

More to Learn

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Suppliers

The RP Photonics Buyer's Guide contains 28 suppliers for wedge prisms. Among them:

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.

Edmund Optics

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

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.

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.

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.

Shalom EO

Shalom EO offers off-the-shelf wedge prisms and custom wedge prisms with high precision which are ideal for laser beam steering. Shalom EO wedge prisms are made of various materials including N-BK7, UV fused silica, Ca_F2, MgF₂, ZnSe, etc. offering 1–10° light deviation. Coating options include uncoated, V coating, a broadband anti-reflection coating (standard 350–700 nm, 650–1050 nm, and 1050–1700 nm), and other custom coatings, which could be deposited at the wedge side or the flat back side to attenuate the disturbance from the ghost image resulting from surface reflection.

Shalom EO is consistent in investing in developing cutting-edge technologies aimed at fostering a strengthful production line. We are capable of presenting high-precision wedge prisms with <λ/10 flatness, <30 arcsec angular tolerance, and +0/–0.1 mm dimension tolerance. Available size options include 25.4 mm diameter for stocked wedge prism or custom.

Sinoptix

We offer bespoke wedge prisms. Up to diameter 500mm in optical glass or fused silica substrate, AR coatings and Lambda/4 surface quality.

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