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Axicons, Zinc Selenide![]()
AX7252-E3 2.0° Physical Angle AX72505-E3 0.5° Physical Angle AX72501-E3 0.1° Physical Angle Axicon Ray Tracing Diagram ![]() Please Wait
![]() Click to Enlarge The diagram above shows the definitions of thicknesses and angles used on this page. Features
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: ![]() 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°.
Axicon Beams
![]() 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. ![]() Figure 2: Axicon ray tracing diagram.
Selection Guide for PrismsThorlabs 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
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Prism | Material | Deviation | Invert | Reverse or Rotate | Illustration | Applications |
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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 |
Compensate for pulse broadening effects in ultrafast laser systems. Can be used as an optical filter, for wavelength tuning, or dispersion compensation.
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Pellin Broca Prisms | N-BK7, UV Fused Silica, or Calcium Fluoride |
90° | 90° | No | ![]() |
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. |
Prism | Material | Deviation | Invert | Reverse or Rotate | Illustration | Applications |
---|---|---|---|---|---|---|
Anamorphic Prism Pairs | N-KZFS8 or N-SF11 |
Variable Vertical Offset | No | No | ![]() |
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 | ![]() |
Creates a conical, non-diverging beam with a Bessel intensity profile from a collimated source. |
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 | ![]() |
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 | ![]() |
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.
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Double Glan-Taylor Polarizers | Calcite | p-pol. - 0° s-pol. absorbed by housing |
No | No | ![]() |
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 | ![]() |
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 | ![]() |
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 |
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. |
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Fresnel Rhomb Retarders | N-BK7 | Linear to circular polarization Vertical Offset |
No | No |
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. |
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Rotates linearly polarized light 90° | No | No |
λ/2 Fresnel Rhomb Retarder rotates linearly polarized light 90°. Uniform λ/2 retardance over a wider wavelength range compared to birefringent wave plates. |
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 |
Double prism configuration and dielectric coating provide 50:50 beamsplitting nearly independent of polarization. Non-polarizing beamsplitter over the specified wavelength range. |
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Polarizing Beamsplitter Cubes | N-BK7, UV Fused Silica, or N-SF1 | p-pol. - 0° s-pol. - 90° |
No | No |
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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