Axicons, Zinc Selenide


  • ZnSe Ideal for IR Applications
  • AR Coated for 7 - 12 µm
  • 1" Diameter
  • Apex Rounding Diameter: <1.0 mm

AX7252-E3

 2.0° Physical Angle

AX72505-E3

0.5° Physical Angle

AX72501-E3

0.1° Physical Angle

Axicon Ray Tracing Diagram

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Common Specifications
Substrate Material Zinc Selenidea
AR Coating Range 7 - 12 µm
Reflectance (per Surface)b 
Ravg < 1%; Rabs < 2%
Transmissionb Tavg > 97%; Tabs > 92%
AR Coating Plotc Axicon Coating
Diameter 1" (25.4 mm)
Diameter Tolerance +0.0 / -0.05 mm
Apex Rounding Diameter (S1) <1.0 mm
Surface Quality (S1, S2) 60-40 Scratch-Dig
Surface Flatness (S2) <λ/2 at 633 nm
Surface Deviation (RMS) (S1) <0.07 µm
Surface Roughness (RMS) (S1,S2) <20 Å
Clear Aperture (S1, S2) >Ø22.86 mm
Edge Thickness 3.4 mm
Center Thickness Tolerance ±0.1 mm
Angular Tolerance ±0.01°
  • Click Link for Detailed Specifications on the Substrate Glass
  • Over AR Coating Range at 0° AOI
  • Coating data is available here.
Axicons Selection Guide
UV Fused Silica Axicons
ZnSe Axicons
Zemax Files
Click on the red Document icon next to the item numbers below to access the Zemax file download. Our entire Zemax Catalog is also available.
Axicon Diagram
Click to Enlarge

The diagram above shows the definitions of thicknesses and angles used on this page.

Features

  • Transform a Collimated Beam into a Ring
  • Five Physical Angles Available: 0.1°, 0.2°, 0.5°, 1.0°, and 2.0°
  • Broadband AR Coating with Ravg <1% from 7 to 12 µm

An axicon, also known as a rotationally symmetric prism, is a lens that features one conical surface and one plano surface. They are commonly used to create a beam with a Bessel intensity profile or a conical, non-diverging beam. When converting a collimated beam into a ring, the plano side of the axicon should face the collimated source.  

These axicons are offered with base angles from 0.1° to 2.0° and are precisely manufactured from zinc selenide (ZnSe), making them ideally suited for mid-infrared laser applications and for use with CO2 laser applications, like materials processing. ZnSe axicons are offered with our -E3 antireflection coating for 7 to 12 µm. The coating is deposited on both sides of each optic in order to improve transmission by reducing surface reflections. Additionally, ZnSe axicons provide enough transmission in the visible region of the spectrum to allow the use of a red alignment beam, such as a HeNe laser.

An axicon deflects light according to Snell's Law, which can be used to find the deflection angle:

Axicon Equation

where n is the index of refraction of the glass, α is the physical angle of the prism, and ß is the angle the deflected beam creates with the optical axis. Here, the refractive index of air is assumed to be 1. This interaction is illustrated in the reference image to the right.

When handling optics, one should always wear gloves. This is especially true when working with zinc selenide, as it is a hazardous material. For your safety, please follow all proper precautions, including wearing gloves when handling these lenses and thoroughly washing your hands afterward. Due to the low hardness of ZnSe, additional care should be taken to not damage these lenses. Click here to download a PDF of the MSDS for ZnSe.

Thorlabs also offers Ø1/2" and Ø1" UV Fused Silica Axicons, either uncoated or with an AR coating, and with physical angles ranging from 0.5° to 40.0°. 

Optic Cleaning Tutorial Optical Coatings and Substrates

Axicon Beams

  • Bessel Beam: Non-Diffracting
  • Ring-Shaped Beam: Ideal for Laser Drilling


Figure 1: The absolute value of a 0th order Bessel function. A true Bessel Beam requires each ring to have the same energy as the central peak, thus an infinite amount of energy is needed.

A Bessel beam is a non-diffracting beam of concentric rings, each having the same power as the central ring. Technically, a Bessel beam cannot be created as it requires infinite energy. A beam closely resembling a Bessel distribution can be generated by passing a Gaussian beam through an axicon and taking the projection of the beam close to the axicon’s conical surface. The absolute value of a 0th order Bessel function of the first kind is shown in Figure 1 (right).

When the beam is projected further from the lens, a single ring-shaped beam is formed. The beam is actually conical (i.e., diameter increases with distance), but the rays are non-diverging so that the thickness of the ring remains constant (see Figure 2). The ring's thickness will be half of the input laser beam's diameter. This type of beam is commonly used in laser-drilling applications.

Axicon Diagram

Figure 2: Axicon ray tracing diagram.

Posted Comments:
Kenneth Robinson  (posted 2021-05-05 09:01:49.227)
I want to generate a bessel beam for a Mid IR laser operating around 2940 nm,m what are the transmission properties of he AR coating in that wavelength range? And do you offer uncoated ZnSe axicons?
YLohia  (posted 2021-05-05 02:26:03.0)
Hello, the AR coating on these is not suited for the 2940 nm range. Uncoated or different AR-coated axicons (for example the -E4 AR coating for your wavelength range) can be requested by clicking on the "Request Quote" button above or by contacting your local Thorlabs Tech Support team (in your case, techsupport.uk@thorlabs.com).
Volker Franke  (posted 2020-12-08 14:24:16.1)
ich habe eine optische Frage an Sie. Ich erstelle gerade Pläne für ein Angebot an einen Industriekunden in dessen Auftrag wir im Erfolgsfall Untersuchungen mit einem ringförmigen Laserstrahl machen wollen. Hierzu benötige ich aber zunächst eine Ein-/Abschätzung zur Machbarkeit. Wir wollen mit einem CO2-Laserstrahl einen relativ großen ringförmigen Fokus generieren. Hier die Eckpunkte zur Orientierung: - Ringdurchmesser Ziel ca. 40 mm - Rindbreite (Linienbreite) sollte möglichst klein sein (was geht?) (Wunsch wäre kleiner als 0,4 mm, besser 0,2 mm) - Arbeitsabstand zwischen Optik und Material sollte groß genug sein um die Optik vor Dreck zu schützen (gefühlt mindestens 100 mm) - Rohstrahldurchmesser ca. 16-18 mm - Geschätzte Laserstrahlleistung ca. 600 – 1500 W (das hängt sehr von der realisierten Ringbreite ab) Wie genau die Optik aufgebaut ist, spielt im Moment noch keine Rolle. Ich vermute man wird mindestens ein Axicon und eine Linse benötigen. Ob die Optiken transmittiv oder reflektiv sind, ist auch erst mal egal. Für erste Tests zur Machbarkeit wollen wir den Aufwand nicht zu groß werden lassen und könnten ggf. ein paar Abstriche von oben genannten Zielwerten machen, wenn dies mit Standardoptiken umsetzbar ist. Gern würde ich mich mit Ihnen austauschen, was machbar ist, damit ich unsere Arbeitspläne und das Angebot weiter ausarbeiten kann. Grundsätzlich denken wir als zweiten Lösungsweg auch darüber nach, das Ganze auch mit einem Faserlaser zu testen. Aufgrund der Absorption im Material wäre der CO2-Laser aber bevorzugt. Über Ihre Rückmeldung und technische Beratung würde ich mich sehr freuen. Mit freundlichen Grüßen Volker Franke
YLohia  (posted 2020-12-08 11:20:43.0)
Hello, thank you for contacting Thorlabs. An applications engineer from our team in Germany (europe@thorlabs.com) will reach out to you directly to discuss this furter.

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-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 (UVFS, ZnSe) 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.

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ZnSe Axicons (AR Coated: 7 µm - 12 µm)

Item # Diameter Physical Angle (α) Deflection Angle (β)a Center Thickness (tc)
AX72501-E3 Ø1"
(Ø25.4 mm)
0.1° 0.14° 3.4 mm
AX72502-E3 0.2° 0.3° 3.4 mm
AX72505-E3 0.5° 0.7° 3.5 mm
AX7251-E3 1.0° 1.4° 3.6 mm
AX7252-E3 2.0° 2.8° 3.8 mm
  • Deflection Angles Calculated for 10.6 µm Light
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+1 Qty Docs Part Number - Universal Price Available
AX72501-E3 Support Documentation
AX72501-E3Customer Inspired! Ø1" Axicon, ZnSe, AR Coated: 7.0 - 12.0 µm, 0.1°
$719.05
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AX72502-E3 Support Documentation
AX72502-E3Customer Inspired! Ø1" Axicon, ZnSe, AR Coated: 7.0 - 12.0 µm, 0.2°
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AX72505-E3 Support Documentation
AX72505-E3Customer Inspired! Ø1" Axicon, ZnSe, AR Coated: 7.0 - 12.0 µm, 0.5°
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AX7251-E3 Support Documentation
AX7251-E3Customer Inspired! Ø1" Axicon, ZnSe, AR Coated: 7.0 - 12.0 µm, 1.0°
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AX7252-E3 Support Documentation
AX7252-E3Customer Inspired! Ø1" Axicon, ZnSe, AR Coated: 7.0 - 12.0 µm, 2.0°
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