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Knife-Edge Right-Angle Prism Mirrors


  • Precision Cut Prisms Feature Bevel-Free 90° Angle
  • Silver, Gold, and Aluminum Coatings Available
  • 25 mm x 25 mm Faces

MRAK25-P01

MRAK25-F01

Application Idea

MRAK25-M01 Mounted  
on a KM100B Kinematic
Platform Mount

Related Items


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Right-Angle Prism Figure
The size of these prisms is defined by the leg dimension, L. See the Specs tab for full product dimensions.
Knife Edge Prism Application
Click to Enlarge

This schematic shows how two beams can be made collinear using these knife-edge right-angle prism mirrors.

Features

  • Right-Angle Prism with Mirror-Coated Legs
  • "Knife Edge" Between the Two Coated Surfaces for Combining or Separating Beams
  • 25 mm x 25 mm Reflective Surfaces

Thorlabs' Knife-Edge Right-Angle Prism Mirrors feature reflective coatings on the two legs and offer a clear aperture extending across the 90° angle between the coated surfaces. They are manufactured from N-BK7 and have 25 mm x 25 mm reflective legs. These prism mirrors are offered with one of the following reflective coatings: UV enhanced aluminum, protected aluminum, protected gold, or protected silver. Please see the Specs and Graphs tabs above for details on the reflectivity of the various coatings.

The precision corner between the two coated surfaces allows two counterpropagating beams to be made collinear with the output orthogonal to the input, as shown in the figure to the right. They can also be used to split a single input beam aimed directly at the knife edge. The prisms are ideal for situations where it is undesirable to use a beamsplitting cube, such as due to the geometry of the setup. Some diffraction and scatter will occur whenever a beam is split using these prisms.

These prisms feature a coating that extends to the edge of the optic. Care should be used when handling the prisms, as the coated edge is very delicate and can be chipped easily.

While the hypotenuse is polished, these mirrors are not intended for use as retroreflectors due to the adhesion layers used in the coating process. As a result, no specifications are given for the polished hypotenuse of the prism. For retroreflection applications we suggest the PS911K, an uncoated version of our knife edge prism, or our selection of mounted and unmounted retroreflectors. Thorlabs also offers a selection of hypotenuse-coated right-angle prism mirrors.

Right Angle Prism Mirror Selection Guide
Hypotenuse Coated
Metallic Coatings (250 nm - 20 µm)
Dielectric Coatings (400 nm - 1100 nm)
Laser Line (532 nm and 1064 nm)
Leg Coated
Knife-Edge, Metallic and Dielectric Coatings
(250 nm - 20 µm)
Dielectric Coatings (400 nm - 1100 nm)

Care and Handling
Silver coated mirrors require additional care due to their susceptibility to damage from environmental conditions and improper handling. Fingerprints, contact with abrasive surfaces, and environments with high humidity or temperature will diminish the effectiveness of the protective overcoat leaving the silver coating susceptible to oxidation and degradation. When working with silver mirrors, follow standard practices for handling optics. Latex gloves or similar protective coverings are recommended to prevent oil and other residues on the user’s fingers from reaching the optical surface. Even with such precautions, care should be taken not to touch the mirrored face or edges. Silver mirrors should be used and stored in areas at room temperature with minimal humidity. For information on how to clean mirrors and other optics, visit our Optic Cleaning Tutorial.

Optic Cleaning Tutorial
Optical Coatings and Substrates
Item # MRAK25-F01 MRAK25-G01 MRAK25-P01 MRAK25-M01
Coating (On Legs) UV Enhanced Aluminum Protected Aluminum Protected Silver Protected Gold
Reflectancea Ravg > 90% (250 -450 nm) Ravg > 90% (450 - 2000 nm)
Ravg > 95% (2 - 20 µm)
Ravg > 97% (450 - 2000 nm)
Ravg > 96% (2 - 20 µm)
Ravg > 96% (800 nm - 20 µm)
Substrate Material N-BK7
Lb  25.0 mm
Xb  35.4 mm
Clear Aperture
(Coated Surfaces)
 Entire Face Length and Width, Excluding a 1.25 mm Border Along All Beveled Edges
Clear Aperture
(Hypotenuse)
90% of Face Length and Width
Surface Flatness
(All Surfaces)
λ/8 @ 632.8 nm Over the Clear Aperture (Peak to Valley) 
Surface Quality 20-10 Scratch-Dig
  • For an angle of incidence from 0° to 45°.
  • Defined in the diagram below.
Prism Schematic
Prism Schematic

All data shown below is for unpolarized light, unless otherwise stated. The shaded regions in the graphs denote the ranges over which we guarantee the specified reflectance. Please note that the reflectance outside of these bands is typical and can vary from lot to lot, especially in out-of-band regions where the reflectance is fluctuating or sloped.

UV-Enhanced Aluminum Coating (250 - 450 nm)

UV-Enhanced Aluminum at Near-Normal Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for UV-Enhanced Aluminum
UV-Enhanced Aluminum at 45 Degree Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for UV-Enhanced Aluminum
UV-Enhanced Aluminum at Near-Normal Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for UV-Enhanced Aluminum
UV-Enhanced Aluminum at 45 Degree Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for UV-Enhanced Aluminum

 

Protected Aluminum Coating (450 nm - 20 µm)

Protected Aluminum at Near-Normal Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for Protected Aluminum
Protected Aluminum at 45 Degree Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for Protected Aluminum

 

Protected Silver Coating (450 nm - 20 µm)

Protected Silver at Near-Normal Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for Protected Silver
Protected Silver at 45 Degree Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for Protected Silver

 

Protected Gold Coating (800 nm - 20 µm)

Protected Gold at Near-Normal Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for Protected Gold
Protected Gold at 45 Degree Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for Protected Gold


Posted Comments:
Lorenz Sykora  (posted 2020-07-23 12:28:32.3)
Is ist possible to get it also with unprotected gold. We are working in the midinfrared region and the absorption of the protected gold for 45° is way to much. 45° would be the standard angle for this optical component.
YLohia  (posted 2020-07-23 02:39:03.0)
Thank you for contacting Thorlabs. Custom optics can be requested by emailing techsupport@thorlabs.com. We will reach out to you to discuss the possibility of offering this customization.
Marshall Scott  (posted 2019-10-21 14:37:34.193)
rstahl (posted 2018-05-01 14:47:00.51) How sharp is the knife edge? How small a beam diameter could I split with this part? YLohia (posted 2018-05-02 10:31:35.0) Hello, unfortunately, we do not specify an exact thickness of the knife edge on these prisms; we design the thickness of the edge as thin as our manufacturing abilities allow and is suited for general beamsplitting and beam combining applications. :(
YLohia  (posted 2019-11-05 03:15:05.0)
We specify no chamfer on this surface to ensure working distance is available as close to the edge as possible. We are currently working on defining a specification as to how sharp that edge actually is. I will reach out to you via e-mail to discuss this further.
lebouquj  (posted 2018-06-07 16:32:10.937)
Hello, Could you offer MRAK20-M01, that is with 20mm legs instead of 25mm ? Thanks, Jean-Baptiste
nbayconich  (posted 2018-06-12 10:15:57.0)
Thank you for contacting Thorlabs. We can look into providing this custom for you. I will reach out to you directly with more information. For any custom requests please contact techsupport@thorlabs.com directly.
simon.neves  (posted 2018-05-03 17:13:22.78)
Dear Sir/Madam, Do you provide a knife edge with dielectric coatic for 1550 nm wavelength ? Thank you for your help Simon Neves
YLohia  (posted 2018-05-04 10:02:31.0)
Dear Simon, thank you for contacting Thorlabs. We do have the ability to provide these knife-edge right-angle prisms with our selection of dielectric coatings as specials. We will contact you directly for more details.
rstahl  (posted 2018-05-01 14:47:00.51)
How sharp is the knife edge? How small a beam diameter could I split with this part?
YLohia  (posted 2018-05-02 10:31:35.0)
Hello, unfortunately, we do not specify an exact thickness of the knife edge on these prisms; we design the thickness of the edge as thin as our manufacturing abilities allow and is suited for general beamsplitting and beam combining applications.
pierrick.cheiney  (posted 2018-04-17 15:59:01.933)
Dear Sir/Madam, Could you provide knife-edge prism mirror in smaller size such as 5 or 10 mm width? Best regards, Pierrick Cheiney
YLohia  (posted 2018-04-17 11:17:46.0)
Hello Pierrick, thank you for contacting Thorlabs. We will reach out to you directly to discuss the possibility of offering this.
yitzhak.malka  (posted 2018-01-31 08:59:18.217)
Can you please indicate the 90degree angle accuracy?
nbayconich  (posted 2018-02-07 04:19:12.0)
Thank you for contacting Thorlabs. The tolerance to the 90 degree angle is ±3 arcminutes.
cmullark  (posted 2018-01-18 05:27:01.987)
I have a question: What is the thickness of the knife-edge? If I place the prism in the focal plane of a beam to split it than as I focus tighter and tighter there will be more scattering/loss determined primarily by the knife edge thickness. Would it be different between the dielectric coating and the protected silver? Thanks for any help you can provide in this matter.
nbayconich  (posted 2018-03-30 04:25:50.0)
Thank you for contacting Thorlabs. We do not specify an exact thickness for either coating type of these knife edge prisms, we design the thickness of the edge as thin as our manufacturing abilities allow.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
MRAK25-F01 Support Documentation
MRAK25-F01Customer Inspired! Knife-Edge Right-Angle Prism UV Enhanced Aluminum Mirror, 250-450 nm, L = 25 mm
$133.10
Today
MRAK25-G01 Support Documentation
MRAK25-G01Customer Inspired! Knife-Edge Right-Angle Prism Prot. Aluminum Mirror, 450 nm-20 µm, L = 25 mm
$133.10
Today
MRAK25-P01 Support Documentation
MRAK25-P01Customer Inspired! Knife-Edge Right-Angle Prism Prot. Silver Mirror, 450 nm-20 µm, L = 25 mm
$133.10
Today
MRAK25-M01 Support Documentation
MRAK25-M01Customer Inspired! Knife-Edge Right-Angle Prism Prot. Gold Mirror, 800 nm-20 µm, L = 25 mm
$133.10
Today
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