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Specular Retroreflector Prisms


  • Backside Gold Coating Minimizes Polarization Change
  • 180° Reflection Inverts Image
  • <3 arcsec Beam Deviation

PS976-M01B

Ø50.0 mm

PS975-M01B

Ø25.4 mm

PS977-M01B

Ø12.7 mm

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Common Specifications
Prism Material N-BK7a Grade A Fine Anneal
Wavelength Rangeb 800 - 2000 nm
Reflective Coating Gold with Black Overpaint
Diameter Tolerance +0.0 / -0.1 mm
Surface Quality 40-20 Scratch-Dig
Front Surface Flatness <λ/10 @ 633 nm
Beam Deviationc <3 arcsec
  • Click Link for Detailed Specifications on the Substrate Glass
  • The wavelength range is limited by the transmission of the N-BK7 substrate and the reflectance of the gold coating.
  • Between Incident and Reflected Beams
Retroreflector General Drawing
Click to Enlarge

Retroreflector Dimensions

Features

  • Fabricated from N-BK7
  • Reflects an Inverted and Reversed Image 180°
  • Specular Design for Polarization Azimuthal Angle Rotation <10°
  • Three Prism Sizes Available:
    • Ø12.7 mm
    • Ø25.4 mm
    • Ø50.0 mm
  • Gold-Coated Reflective Faces with Black Overpaint
  • 800 - 2000 nm Wavelength Range
Optical Coatings and Substrates
Optic Cleaning Tutorial

These unmounted retroreflectors are trihedral prisms manufactured from a solid piece of N-BK7 glass. They are backside coated and employ second-surface specular reflections, which minimize changes in polarization and introduced ellipticity; retroreflectors with uncoated reflective faces rely on total internal reflection (TIR), which affects the polarization state considerably. Commonly referred to as corner cubes, the prisms sold here are available in three different sizes (Ø12.7 mm, Ø25.4 mm, and Ø50.0 mm). They are often used with translation stages to create optical delay lines.

Retroreflector in Fixed Mount
Click to Enlarge

PS975-M01B Retroreflector Mounted in FMP1 Fixed Optic Mount
The video above shows the beam path through a retroreflector.

Retroreflector Prisms
Retroreflectors reflect an image or beam back toward its original direction via three reflections. The beam or image will be inverted and reflected through 180° even if the angle of incidence is not zero. The insensitivity of the alignment of these prisms make them ideal retroreflecting optics. For these retroreflecting prisms, the incident and reflected beams will be parallel to within 3 arcsec. However, unless the incident and reflected beams strike the exact center of the optic, they will not overlap but rather be shifted with respect to each other. For example, if the incident beam strikes the optic 3 mm to the right of center, the retroreflected beam will emerge 3 mm to the left of center. The prisms are able to retroreflect beams as large as the maximum beam diameter listed in the table below.

The second-surface gold coating on these prisms also has protective black overpaint that resists fingerprints and mild solvents.

Mounting
Each retroreflector is also offered mounted in an SM-threaded lens tube for easy integration into an optical system. However, if you wish to mount our unmounted retroreflectors, we suggest either our V-mounts or our fixed optical mounts, which use a nylon-tipped setscrew to secure the retroreflector.

Please refer to the Prism Guide tab above for assistance in selecting the appropriate prism for your application.

N-BK7 Transmission
Click to Enlarge

Click Here for Raw Data
This graph shows the transmission of an N-BK7 substrate that is 10 mm thick. Note that losses are lower wavelengths are predominantly due to Fresnel reflections and material absorption losses become pronounced at higher wavelengths.
Protected Gold Reflectance
Click to Enlarge

Click Here for Raw Data
This graph shows the reflectance of a protected gold coating at 45° AOI.
Zemax Simulation of Retro Reflectance
Click to Enlarge

This graph shows theoretical data for three sizes of N-BK7 retroreflectors with second-surface gold coatings. Note that the reflectance decreases at higher wavelengths and larger prisms due to longer path lengths through the substrate.

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Selection Guide for Prisms

Thorlabs offers a wide variety of prisms, which can be used to reflect, invert, rotate, disperse, steer, and collimate light. For prisms and substrates not listed below, please contact Tech Support.

Beam Steering Prisms

Prism Material Deviation Invert Reverse or Rotate Illustration Applications
Right Angle Prisms N-BK7, UV Fused Silica, Calcium Fluoride, or Zinc Selenide 90° 90° No 1

90° reflector used in optical systems such as telescopes and periscopes.

180° 180° No 1

180° reflector, independent of entrance beam angle.

Acts as a non-reversing mirror and can be used in binocular configurations.

TIR Retroreflectors
(Unmounted and Mounted)
and Specular Retroreflectors
(Unmounted and Mounted)
N-BK7 180° 180° No Retroreflector

180° reflector, independent of entrance beam angle.

Beam alignment and beam delivery. Substitute for mirror in applications where orientation is difficult to control.

Unmounted Penta Prisms
and
Mounted Penta Prisms
N-BK7 90° No No 1

90° reflector, without inversion or reversal of the beam profile.

Can be used for alignment and optical tooling.

Roof Prisms N-BK7 90° 90° 180o Rotation 1

90° reflector, inverted and rotated (deflected left to right and top to bottom).

Can be used for alignment and optical tooling.

Unmounted Dove Prisms
and
Mounted Dove Prisms
N-BK7 No 180° 2x Prism Rotation 1

Dove prisms may invert, reverse, or rotate an image based on which face the light is incident on.

Prism in a beam rotator orientation.

180° 180° No 1

Prism acts as a non-reversing mirror.

Same properties as a retroreflector or right angle (180° orientation) prism in an optical setup.

Wedge Prisms N-BK7 Models Available from 2° to 10° No No 1

Beam steering applications.

By rotating one wedged prism, light can be steered to trace the circle defined by 2 times the specified deviation angle.

No No Wedge Prism Pair

Variable beam steering applications.

When both wedges are rotated, the beam can be moved anywhere within the circle defined by 4 times the specified deviation angle.

Coupling Prisms Rutile (TiO2) or GGG Variablea No No Coupling Prism

High index of refraction substrate used to couple light into films.

Rutile used for nfilm > 1.8

GGG used for nfilm < 1.8

  • Depends on Angle of Incidence and Index of Refraction


Dispersive Prisms

Prism Material Deviation Invert Reverse or Rotate Illustration Applications
Equilateral Prisms F2, N-SF11, Calcium Fluoride,
or Zinc Selenide
Variablea No No

Dispersion prisms are a substitute for diffraction gratings.

Use to separate white light into visible spectrum.

Dispersion Compensating Prism Pairs Fused Silica, Calcium Fluoride, SF10, or N-SF14 Variable Vertical Offset No No Dispersion-Compensating Prism Pair

Compensate for pulse broadening effects in ultrafast laser systems.

Can be used as an optical filter, for wavelength tuning, or dispersion compensation.

 

Pellin Broca Prisms N-BK7,
UV Fused Silica,
or Calcium Fluoride
90° 90° No 1

Ideal for wavelength separation of a beam of light, output at 90°.

Used to separate harmonics of a laser or compensate for group velocity dispersion.

  • Depends on Angle of Incidence and Index of Refraction

Beam Manipulating Prisms

Prism Material Deviation Invert Reverse or Rotate Illustration Applications
Anamorphic Prism Pairs N-KZFS8 or
N-SF11
Variable Vertical Offset No No 1

Variable magnification along one axis.

Collimating elliptical beams (e.g., laser diodes)

Converts an elliptical beam into a circular beam by magnifying or contracting the input beam in one axis.

Axicons UV Fused Silica
or Zinc Selenide
Variablea No No 1

Creates a conical, non-diverging beam with a Bessel intensity profile from a collimated source.

  • Depends on Prism Physical Angle

Polarization Altering Prisms

Prism Material Deviation Invert Reverse or Rotate Illustration Applications
Glan-Taylor, Glan-Laser, and α-BBO Glan-Laser Polarizers Glan-Taylor:
Calcite

Glan-Laser:
α-BBO or Calcite
p-pol. - 0°

s-pol. - 112°a
No No Glan-Taylor Polarizer

Double prism configuration and birefringent calcite produce extremely pure linearly polarized light.

Total Internal Reflection of s-pol. at the gap between the prism while p-pol. is transmitted.

Rutile Polarizers Rutile (TiO2) s-pol. - 0°

p-pol. absorbed by housing
No No Rutile Polarizer Diagram

Double prism configuration and birefringent rutile (TiO2) produce extremely pure linearly polarized light.

Total Internal Reflection of p-pol. at the gap between the prisms while s-pol. is transmitted.

 

Double Glan-Taylor Polarizers Calcite p-pol. - 0°

s-pol. absorbed by housing
No No Glan-Taylor Polarizer

Triple prism configuration and birefringent calcite produce maximum polarized field over a large half angle.

Total Internal Reflection of s-pol. at the gap between the prism while p-pol. is transmitted.

Glan Thompson Polarizers Calcite p-pol. - 0°

s-pol. absorbed by housing
No No Glan-Thompson Polarizer

Double prism configuration and birefringent calcite produce a polarizer with the widest field of view while maintaining a high extinction ratio.

Total Internal Reflection of s-pol. at the gap between the prism while p-pol. is transmitted.

Wollaston Prisms and
Wollaston Polarizers
Quartz, Magnesium Fluoride, α-BBO, Calcite, Yttrium Orthovanadate Symmetric
p-pol. and
s-pol. deviation angle
No No Wollaston Prism

Double prism configuration and birefringent calcite produce the widest deviation angle of beam displacing polarizers.

s-pol. and p-pol. deviate symmetrically from the prism. Wollaston prisms are used in spectrometers and polarization analyzers.

Rochon Prisms Magnesium Fluoride
or
Yttrium Orthovanadate
Ordinary Ray: 0°

Extraordinary Ray: deviation angle
No No

Double prism configuration and birefringent MgF2 or YVO4 produce a small deviation angle with a high extinction ratio.

Extraordinary ray deviates from the input beam's optical axis, while ordinary ray does not deviate.

Beam Displacing Prisms Calcite 2.7 or 4.0 mm Beam Displacement No No Beam Displacing Prism

Single prism configuration and birefringent calcite separate an input beam into two orthogonally polarized output beams.

s-pol. and p-pol. are displaced by 2.7 or 4.0 mm. Beam displacing prisms can be used as polarizing beamsplitters where 90o separation is not possible.

Fresnel Rhomb Retarders N-BK7 Linear to circular polarization

Vertical Offset
No No Fresnel Rhomb Quarter Wave

λ/4 Fresnel Rhomb Retarder turns a linear input into circularly polarized output.

Uniform λ/4 retardance over a wider wavelength range compared to birefringent wave plates.

Rotates linearly polarized light 90° No No Fresnel Rhomb Half Wave

λ/2 Fresnel Rhomb Retarder rotates linearly polarized light 90°.

Uniform λ/2 retardance over a wider wavelength range compared to birefringent wave plates.

  • S-polarized light is not pure and contains some P-polarized reflections.

Beamsplitter Prisms

Prism Material Deviation Invert Reverse or Rotate Illustration Applications
Beamsplitter Cubes N-BK7 50:50 splitting ratio, 0° and 90°

s- and p- pol. within 10% of each other
No No Non-polarizing Beamsplitter

Double prism configuration and dielectric coating provide 50:50 beamsplitting nearly independent of polarization.

Non-polarizing beamsplitter over the specified wavelength range.

Polarizing Beamsplitter Cubes N-BK7, UV Fused Silica, or N-SF1 p-pol. - 0°

s-pol. - 90°
No No Polarizing Beamsplitter Cube

Double prism configuration and dielectric coating transmit p-pol. light and reflect s-pol. light.

For highest polarization use the transmitted beam.

Retroreflector Prisms, Gold-Coated Reflective Faces

Item # Wavelength Range Theoretical
Reflectancea
Clear Aperture Length (L)b Diameter (D)b Max Beam
Diameterc
Reference
Diagram
PS977-M01B 800 - 2000 nm Theoretical Reflectance >Ø8.9 mm 11.4 mm Ø12.7 mm Ø0.16" (4.085 mm) info
PS975-M01B >Ø17.8 mm 21.9 mm Ø25.4 mm Ø0.32" (8.125 mm)
PS976-M01B >Ø35.0 mm 41.9 mm Ø50.0 mm Ø0.64" (16.256 mm)
  • See the Graphs tab for details.
  • Dimensions Given as Defined in the Reference Diagram
  • This is the maximum accepted beam diameter for each of the three prism faces at 0° AOI.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
PS977-M01B Support Documentation
PS977-M01BNEW!Specular Retroreflector, Ø12.7 mm, L = 11.4 mm, Gold Coating: 800 - 2000 nm
$158.00
Today
PS975-M01B Support Documentation
PS975-M01BNEW!Specular Retroreflector, Ø25.4 mm, L = 21.9 mm, Gold Coating: 800 - 2000 nm
$190.00
Today
PS976-M01B Support Documentation
PS976-M01BNEW!Specular Retroreflector, Ø50.0 mm, L = 41.9 mm, Gold Coating: 800 - 2000 nm
$253.00
5-8 Days
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