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Anamorphic Prism Pairs


  • Transform Elliptical Laser Diode Beams Into Nearly Circular Beams
  • Magnification from 2.0 to 4.0
  • Three Broadband AR Coating Choices

PS879-A

Mounted, Pre-Aligned Prism Pair

SM05
Threading

PS871-B

Unmounted Prism Pair

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General Specifications
Material N-SF11a (Uncoated, -B, -C)
N-KZFS8a (-A Coating)
Dimensional
Tolerances
±0.15 mm
Angular
Tolerances
±15 arcmin
Maximum Input
Beam Size
Unmounted: Ø9.9 mm
Mounted: 5.1 mm Minor Axis, 9.9 mm Major Axis
Maximum Output
Beam Size
Ø9.9 mm
Surface Flatness λ/10 @ 633 nm
Surface Quality 40-20 Scratch-Dig
Coating Options Uncoated
AR Coated: 350 - 700 nm (-A)
AR Coated: 650 - 1050 nm (-B)
AR Coated: 1050 - 1700 nm (-C)
Material Damage
Threshold
N-KZFS8 -A Coating: 5 J/cm2
(532 nm, 10 ns, 10 Hz, Ø0.456 mm)
N-SF11 -B Coating: 10 J/cm2
(1064 nm, 10 ns, 10 Hz, Ø0.454 mm)
N-SF11 -C Coating: 10 J/cm2
(1064 nm, 10 ns, 10 Hz, Ø0.521 mm)
  • Click Link for Detailed Specifications on the Substrate Glass

Thorlabs' Anamorphic Prism Pairs are used to transform elliptical laser diode beams into nearly circular beams by magnifying the elliptical beam in one dimension. They can also be used to convert a circular beam into an elliptical beam. Available unmounted or mounted in Ø1" housings that feature SM05 (0.535"-40) threads on one end, these prism pairs can be purchased uncoated (unmounted only) or with an antireflection coating for the 350 - 700 nm, 650 - 1050 nm, or 1050 - 1700 nm spectral ranges. Mounted prisms can be chosen with magnifications from 2.0 to 4.0.

An average throughput of 95% can be achieved if the prisms are oriented such that the incident light enters the prism pair at Brewster's angle and each surface has the appropriate AR coating for the wavelength of the incident light. Please note that the maximum input beam width is 90% of the prism width. For the mounted prisms, the maximum input beam height is given by the entrance opening height.

Beam shaping can also be accomplished by using cylindrical lenses, which provide one-dimensional shaping of a beam. For more information about Thorlabs' extensive line of prisms, please refer to the Prism Guide tab above.

Optic Cleaning Tutorial
Schematic of Unmounted Anamorphic Prism Pairs
Schematic of Mounted Anamorphic Prism Pairs
L is the displacement between the input and output apertures and is given in the tables below. Please note that the output beam will not exit at the center of the aperture.

N-KZFS8 Reflectance and Transmission


N-SF11 Reflectance and Transmission

N-SF11 Transmission
Click Here for Raw Data
Click to Enlarge

The graphs below show the magnification factor as a function of wavelength for all of our mounted anamorphic prism pairs.

Anamorphic Prism Pair Dependence on Angle

Prism Ray Diagram


The plots below show the angles at which the prisms must be set for various magnifications:

Prism Angles: -A Coating
Prism Angles: -B and -C Coatings
Beam Circularization Setup
Click to Enlarge

 The beam circularization systems were placed in the area of the experimental setup highlighted by the yellow rectangle.
Spatial Filter Setup
Click to Enlarge

Spatial Filter System
Anamorphic Prism Pair Setup
Click to Enlarge

Anamorphic Prism Pair System
Cylindrical Lens Pair Setup
Click to Enlarge

Cylindrical Lens Pair System

Comparison of Circularization Techniques for Elliptical Beams

Edge-emitting laser diodes emit elliptical beams as a consequence of the rectangular cross sections of their emission apertures. The component of the beam corresponding to the narrower dimension of the aperture has a greater divergence angle than the orthogonal beam component. As one component diverges more rapidly than the other, the beam shape is elliptical rather than circular. 

Elliptical beam shapes can be undesirable, as the spot size of the focused beam is larger than if the beam were circular, and larger spot sizes have lower irradiances (power per area). Several different techniques can be used to circularize an elliptical beam, and we experimented with and compared the performance of three methods based on a pair of cylindrical lenses, an anamorphic prism pair, and a spatial filter. The characteristics of the circularized beams were evaluated by performing M2 measurements, wavefront measurements, and measuring the transmitted power. 

While we demonstrated that each circularization technique improves the circularity of the elliptical input beam, we showed that each technique provides a different balance of circularization, beam quality, and transmitted power. Our results, which are documented in this Lab Fact, indicate that an application's specific requirements will determine which is the best circularization technique to choose.

Experimental Design and Setup

The experimental setup is shown in the picture at the top-right. The elliptically-shaped, collimated beam of a temperature-stabilized 670 nm laser diode was input to each of our circularization systems. Collimation results in a low-divergence beam, but it does not affect the beam shape.

The beam circularization systems, shown to the right, were placed, one at a time, in the vacant spot in the setup highlighted by the yellow rectangle. With this arrangement, it was possible to use the same experimental conditions when evaluating each circularization technique, which allowed the performance of each to be directly compared with the others. Some information describing selection and configuration procedures for several components used in this experimental work can be accessed by clicking the following hyperlinks: 

The characteristics of the beams output by the different circularization systems were evaluated by making measurements using a power meter, a wavefront sensor, and an M2 system. In the image of the experimental setup, all of these systems are shown on the right side of the table for illustrative purposes; they were used one at a time. The power meter was used to determine how much the beam circularization system attenuated the intensity of the input laser beam. The wavefront sensor provided a way to measure the abberations of the output beam. The M2 system measurement describes the resemblence of the output beam to a Gaussian beam. Ideally, the circularization systems would not attenuate or abberate the laser beam, and they would output a perfectly Gaussian beam. 

Edge-emitting laser diodes also emit astigmatic beams, and it can be desirable to force the displaced focal points of the orthogonal beam components to overlap. Of the three circularization techniques investigated in this work, only the cylindrical lens pair can also compensate for astigmatism. The displacement between the focal spots of the orthogonal beam components were measured for each circularization technique. In the case of the cylindrical lens pair, their configuration was tuned to minimize the astigmatism in the laser beam. The astigmatism was reported as a normalized quantity.

Experimental Results

The experimental results are summarized in the following table, in which the green cells identify the best result in each category. Each circularization approach has its benefits. The best circularization technique for an application is determined by the system’s requirements for beam quality, transmitted optical power, and setup constraints. 

Spatial filtering significantly improved the circularity and quality of the beam, but the beam had low transmitted power. The cylindrical lens pair provided a well-circularized beam and balanced circularization and beam quality with transmitted power. In addition, the cylindrical lens pair compensated for much of the beam's astigmatism. The circularity of the beam provided by the anamorphic prism pair compared well to that of the cylindrical lens pair. The beam output from the prisms had better M2 values and less wavefront error than the cylindrical lenses, but the transmitted power was lower. 

Method Beam Intensity Profile Circularitya M2 Values RMS Wavefront Transmitted Power Normalized 
Astigmatismb
Collimated Source Output
(No Circularization Technique)
Collimated
Click to Enlarge

Scale in Microns
0.36 X Axis: 1.28
Y Axis: 1.63
0.17 Not Applicable 0.67
Cylindrical Lens Pair Cylindrical
Click to Enlarge

Scale in Microns
0.84 X Axis: 1.90
Y Axis: 1.93
0.30 91% 0.06
Anamorphic Prism Pair Anamorphic
Click to Enlarge

Scale in Microns
0.82 X Axis: 1.60
Y Axis: 1.46
0.16 80% 1.25
Spatial Filter Spatial
Click to Enlarge

Scale in Microns
0.93 X Axis: 1.05
Y Axis: 1.10
0.10 34% 0.36
  • Circularity=dminor/dmajor, where dminor and dmajor are minor and major diameters of fitted ellipse (1/e intensity) and Circularity = 1 indicates a perfectly circular beam.
  • Normalized astigmatism is the difference in the waist positions of the two orthogonal components of the beam, divided by the Raleigh length of the beam component with the smaller waist.

Components used in each circularization system were chosen to allow the same experimental setup be used for all experiments. This had the desired effect of allowing the results of all circularization techniques to be directly compared; however, optimizing the setup for a circularization technique could have improved its performance. The mounts used for the collimating lens and the anamorphic prism pair enabled easy manipulation and integration into this experimental system. It is possible that using smaller mounts would improve results by allowing the members of each pair to be more precisely positioned with respect to one another. In addition, using made-to-order cylindrical lenses with customized focal lengths may have improved the results of the cylindrical lens pair circularization system. All results may have been affected by the use of the beam profiler software algorithm to determine the beam radii used in the circularity calculation.

Damage Threshold Specifications
Coating Designation
(Item # Suffix)
Substrate
Material
Damage Threshold
-A N-KZFS8 5 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.456 mm)
-B N-SF11 10 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø0.454 mm)
-C N-SF11 10 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø0.521 mm)

Damage Threshold Data for Thorlabs' Anamorphic Prism Pairs

The specifications to the right are measured data for Thorlabs' anamorphic prism pairs. Damage threshold specifications are constant for a given coating, regardless of the magnification or mounting option of the prism.

 

Laser Induced Damage Threshold Tutorial

The following is a general overview of how laser induced damage thresholds are measured and how the values may be utilized in determining the appropriateness of an optic for a given application. When choosing optics, it is important to understand the Laser Induced Damage Threshold (LIDT) of the optics being used. The LIDT for an optic greatly depends on the type of laser you are using. Continuous wave (CW) lasers typically cause damage from thermal effects (absorption either in the coating or in the substrate). Pulsed lasers, on the other hand, often strip electrons from the lattice structure of an optic before causing thermal damage. Note that the guideline presented here assumes room temperature operation and optics in new condition (i.e., within scratch-dig spec, surface free of contamination, etc.). Because dust or other particles on the surface of an optic can cause damage at lower thresholds, we recommend keeping surfaces clean and free of debris. For more information on cleaning optics, please see our Optics Cleaning tutorial.

Testing Method

Thorlabs' LIDT testing is done in compliance with ISO/DIS11254 and ISO 21254 specifications.

First, a low-power/energy beam is directed to the optic under test. The optic is exposed in 10 locations to this laser beam for 30 seconds (CW) or for a number of pulses (pulse repetition frequency specified). After exposure, the optic is examined by a microscope (~100X magnification) for any visible damage. The number of locations that are damaged at a particular power/energy level is recorded. Next, the power/energy is either increased or decreased and the optic is exposed at 10 new locations. This process is repeated until damage is observed. The damage threshold is then assigned to be the highest power/energy that the optic can withstand without causing damage. A histogram such as that below represents the testing of one BB1-E02 mirror.

LIDT metallic mirror
The photograph above is a protected aluminum-coated mirror after LIDT testing. In this particular test, it handled 0.43 J/cm2 (1064 nm, 10 ns pulse, 10 Hz, Ø1.000 mm) before damage.
LIDT BB1-E02
Example Test Data
Fluence # of Tested Locations Locations with Damage Locations Without Damage
1.50 J/cm2 10 0 10
1.75 J/cm2 10 0 10
2.00 J/cm2 10 0 10
2.25 J/cm2 10 1 9
3.00 J/cm2 10 1 9
5.00 J/cm2 10 9 1

According to the test, the damage threshold of the mirror was 2.00 J/cm2 (532 nm, 10 ns pulse, 10 Hz, Ø0.803 mm). Please keep in mind that these tests are performed on clean optics, as dirt and contamination can significantly lower the damage threshold of a component. While the test results are only representative of one coating run, Thorlabs specifies damage threshold values that account for coating variances.

Continuous Wave and Long-Pulse Lasers

When an optic is damaged by a continuous wave (CW) laser, it is usually due to the melting of the surface as a result of absorbing the laser's energy or damage to the optical coating (antireflection) [1]. Pulsed lasers with pulse lengths longer than 1 µs can be treated as CW lasers for LIDT discussions.

When pulse lengths are between 1 ns and 1 µs, laser-induced damage can occur either because of absorption or a dielectric breakdown (therefore, a user must check both CW and pulsed LIDT). Absorption is either due to an intrinsic property of the optic or due to surface irregularities; thus LIDT values are only valid for optics meeting or exceeding the surface quality specifications given by a manufacturer. While many optics can handle high power CW lasers, cemented (e.g., achromatic doublets) or highly absorptive (e.g., ND filters) optics tend to have lower CW damage thresholds. These lower thresholds are due to absorption or scattering in the cement or metal coating.

Linear Power Density Scaling

LIDT in linear power density vs. pulse length and spot size. For long pulses to CW, linear power density becomes a constant with spot size. This graph was obtained from [1].

Intensity Distribution

Pulsed lasers with high pulse repetition frequencies (PRF) may behave similarly to CW beams. Unfortunately, this is highly dependent on factors such as absorption and thermal diffusivity, so there is no reliable method for determining when a high PRF laser will damage an optic due to thermal effects. For beams with a high PRF both the average and peak powers must be compared to the equivalent CW power. Additionally, for highly transparent materials, there is little to no drop in the LIDT with increasing PRF.

In order to use the specified CW damage threshold of an optic, it is necessary to know the following:

  1. Wavelength of your laser
  2. Beam diameter of your beam (1/e2)
  3. Approximate intensity profile of your beam (e.g., Gaussian)
  4. Linear power density of your beam (total power divided by 1/e2 beam diameter)

Thorlabs expresses LIDT for CW lasers as a linear power density measured in W/cm. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size, as demonstrated by the graph to the right. Average linear power density can be calculated using the equation below. 

The calculation above assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).

Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm):

CW Wavelength Scaling

While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application. 

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information.

Pulsed Lasers

As previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the relevant pulse lengths for our specified LIDT values.

Pulses shorter than 10-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism [2]. In contrast, pulses between 10-7 s and 10-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application.

Pulse Duration t < 10-9 s 10-9 < t < 10-7 s 10-7 < t < 10-4 s t > 10-4 s
Damage Mechanism Avalanche Ionization Dielectric Breakdown Dielectric Breakdown or Thermal Thermal
Relevant Damage Specification No Comparison (See Above) Pulsed Pulsed and CW CW

When comparing an LIDT specified for a pulsed laser to your laser, it is essential to know the following:

Energy Density Scaling

LIDT in energy density vs. pulse length and spot size. For short pulses, energy density becomes a constant with spot size. This graph was obtained from [1].

  1. Wavelength of your laser
  2. Energy density of your beam (total energy divided by 1/e2 area)
  3. Pulse length of your laser
  4. Pulse repetition frequency (prf) of your laser
  5. Beam diameter of your laser (1/e2 )
  6. Approximate intensity profile of your beam (e.g., Gaussian)

The energy density of your beam should be calculated in terms of J/cm2. The graph to the right shows why expressing the LIDT as an energy density provides the best metric for short pulse sources. In this regime, the LIDT given as an energy density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now adjust this energy density to account for hotspots or other nonuniform intensity profiles and roughly calculate a maximum energy density. For reference a Gaussian beam typically has a maximum energy density that is twice that of the 1/e2 beam.

Now compare the maximum energy density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately [3]. A good rule of thumb is that the damage threshold has an inverse square root relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 1 J/cm2 at 1064 nm scales to 0.7 J/cm2 at 532 nm):

Pulse Wavelength Scaling

You now have a wavelength-adjusted energy density, which you will use in the following step.

Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm², scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT [4]. For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects.

The pulse length must now be compensated for. The longer the pulse duration, the more energy the optic can handle. For pulse widths between 1 - 100 ns, an approximation is as follows:

Pulse Length Scaling

Use this formula to calculate the Adjusted LIDT for an optic based on your pulse length. If your maximum energy density is less than this adjusted LIDT maximum energy density, then the optic should be suitable for your application. Keep in mind that this calculation is only used for pulses between 10-9 s and 10-7 s. For pulses between 10-7 s and 10-4 s, the CW LIDT must also be checked before deeming the optic appropriate for your application.

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. Contact Tech Support for more information.


[1] R. M. Wood, Optics and Laser Tech. 29, 517 (1998).
[2] Roger M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, Philadelphia, PA, 2003).
[3] C. W. Carr et al., Phys. Rev. Lett. 91, 127402 (2003).
[4] N. Bloembergen, Appl. Opt. 12, 661 (1973).

In order to illustrate the process of determining whether a given laser system will damage an optic, a number of example calculations of laser induced damage threshold are given below. For assistance with performing similar calculations, we provide a spreadsheet calculator that can be downloaded by clicking the button to the right. To use the calculator, enter the specified LIDT value of the optic under consideration and the relevant parameters of your laser system in the green boxes. The spreadsheet will then calculate a linear power density for CW and pulsed systems, as well as an energy density value for pulsed systems. These values are used to calculate adjusted, scaled LIDT values for the optics based on accepted scaling laws. This calculator assumes a Gaussian beam profile, so a correction factor must be introduced for other beam shapes (uniform, etc.). The LIDT scaling laws are determined from empirical relationships; their accuracy is not guaranteed. Remember that absorption by optics or coatings can significantly reduce LIDT in some spectral regions. These LIDT values are not valid for ultrashort pulses less than one nanosecond in duration.

Intensity Distribution
A Gaussian beam profile has about twice the maximum intensity of a uniform beam profile.

CW Laser Example
Suppose that a CW laser system at 1319 nm produces a 0.5 W Gaussian beam that has a 1/e2 diameter of 10 mm. A naive calculation of the average linear power density of this beam would yield a value of 0.5 W/cm, given by the total power divided by the beam diameter:

CW Wavelength Scaling

However, the maximum power density of a Gaussian beam is about twice the maximum power density of a uniform beam, as shown in the graph to the right. Therefore, a more accurate determination of the maximum linear power density of the system is 1 W/cm.

An AC127-030-C achromatic doublet lens has a specified CW LIDT of 350 W/cm, as tested at 1550 nm. CW damage threshold values typically scale directly with the wavelength of the laser source, so this yields an adjusted LIDT value:

CW Wavelength Scaling

The adjusted LIDT value of 350 W/cm x (1319 nm / 1550 nm) = 298 W/cm is significantly higher than the calculated maximum linear power density of the laser system, so it would be safe to use this doublet lens for this application.

Pulsed Nanosecond Laser Example: Scaling for Different Pulse Durations
Suppose that a pulsed Nd:YAG laser system is frequency tripled to produce a 10 Hz output, consisting of 2 ns output pulses at 355 nm, each with 1 J of energy, in a Gaussian beam with a 1.9 cm beam diameter (1/e2). The average energy density of each pulse is found by dividing the pulse energy by the beam area:

Pulse Energy Density

As described above, the maximum energy density of a Gaussian beam is about twice the average energy density. So, the maximum energy density of this beam is ~0.7 J/cm2.

The energy density of the beam can be compared to the LIDT values of 1 J/cm2 and 3.5 J/cm2 for a BB1-E01 broadband dielectric mirror and an NB1-K08 Nd:YAG laser line mirror, respectively. Both of these LIDT values, while measured at 355 nm, were determined with a 10 ns pulsed laser at 10 Hz. Therefore, an adjustment must be applied for the shorter pulse duration of the system under consideration. As described on the previous tab, LIDT values in the nanosecond pulse regime scale with the square root of the laser pulse duration:

Pulse Length Scaling

This adjustment factor results in LIDT values of 0.45 J/cm2 for the BB1-E01 broadband mirror and 1.6 J/cm2 for the Nd:YAG laser line mirror, which are to be compared with the 0.7 J/cm2 maximum energy density of the beam. While the broadband mirror would likely be damaged by the laser, the more specialized laser line mirror is appropriate for use with this system.

Pulsed Nanosecond Laser Example: Scaling for Different Wavelengths
Suppose that a pulsed laser system emits 10 ns pulses at 2.5 Hz, each with 100 mJ of energy at 1064 nm in a 16 mm diameter beam (1/e2) that must be attenuated with a neutral density filter. For a Gaussian output, these specifications result in a maximum energy density of 0.1 J/cm2. The damage threshold of an NDUV10A Ø25 mm, OD 1.0, reflective neutral density filter is 0.05 J/cm2 for 10 ns pulses at 355 nm, while the damage threshold of the similar NE10A absorptive filter is 10 J/cm2 for 10 ns pulses at 532 nm. As described on the previous tab, the LIDT value of an optic scales with the square root of the wavelength in the nanosecond pulse regime:

Pulse Wavelength Scaling

This scaling gives adjusted LIDT values of 0.08 J/cm2 for the reflective filter and 14 J/cm2 for the absorptive filter. In this case, the absorptive filter is the best choice in order to avoid optical damage.

Pulsed Microsecond Laser Example
Consider a laser system that produces 1 µs pulses, each containing 150 µJ of energy at a repetition rate of 50 kHz, resulting in a relatively high duty cycle of 5%. This system falls somewhere between the regimes of CW and pulsed laser induced damage, and could potentially damage an optic by mechanisms associated with either regime. As a result, both CW and pulsed LIDT values must be compared to the properties of the laser system to ensure safe operation.

If this relatively long-pulse laser emits a Gaussian 12.7 mm diameter beam (1/e2) at 980 nm, then the resulting output has a linear power density of 5.9 W/cm and an energy density of 1.2 x 10-4 J/cm2 per pulse. This can be compared to the LIDT values for a WPQ10E-980 polymer zero-order quarter-wave plate, which are 5 W/cm for CW radiation at 810 nm and 5 J/cm2 for a 10 ns pulse at 810 nm. As before, the CW LIDT of the optic scales linearly with the laser wavelength, resulting in an adjusted CW value of 6 W/cm at 980 nm. On the other hand, the pulsed LIDT scales with the square root of the laser wavelength and the square root of the pulse duration, resulting in an adjusted value of 55 J/cm2 for a 1 µs pulse at 980 nm. The pulsed LIDT of the optic is significantly greater than the energy density of the laser pulse, so individual pulses will not damage the wave plate. However, the large average linear power density of the laser system may cause thermal damage to the optic, much like a high-power CW beam.

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, Germanium, 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.

Unmounted Retroreflectors
and
Mounted Retroreflectors

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 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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Posted Comments:
Poster:rsubkh
Posted Date:2016-10-05 09:23:25.267
Dear Sirs, I would like to know what is the optical transmission of the pair of anamorphic prisms at 355nm with AR coating applied. Kind regards, Ruslan
Poster:jlow
Posted Date:2016-10-05 02:20:24.0
Response from Jeremy at Thorlabs: The transmission is estimated to be around 70% at 355nm.
Poster:volker
Posted Date:2016-06-17 16:03:09.493
would you be able to supply the prisms with no coating on the surface with Brewster angle incidence? We are planning to use them intra-cavity in a laser system, where we found that the losses of the AR coating at the Brewster side are too high >3% One the side with 0degree AOI we still require the AR coating.
Poster:besembeson
Posted Date:2016-06-21 02:40:44.0
Response from Bweh at Thorlabs USA: Yes this is possible. I will contact you.
Poster:quig5862
Posted Date:2016-05-30 23:10:02.46
Hi i dont know much about optics. lenses, etc. But would anything u sell be of use for a Home projector. Basically I'm looking for a cheap option to view 21:9 content with a 16:9 projector and read that you can use prism lens for horizontal stretching.
Poster:besembeson
Posted Date:2016-06-02 01:12:34.0
Response from Bweh at Thorlabs USA: In principle you can, as these are designed to stretch a beam or image rays in one direction. But the ones we carry are mostly designed for laboratory use to stretch the elliptical output from a diode laser in one direction. You will have to construct an imaging system to achieve that.
Poster:gotodani
Posted Date:2016-02-01 03:04:16.873
Hello We are currently using the Anamorphic Prism Pairs (PS879-B) for beam shaping of two lasers (766 and 780 nm). Both lasers are combined before entering the prism pairs. Our question is will these two lasers (which are combined into one single beam) be separated into two beams after passing through the prism pairs because of the diffraction?
Poster:besembeson
Posted Date:2016-02-04 11:41:23.0
Response from Bweh at Thorlabs USA: Yes this will happen. The magnification is also wavelength dependent so the beams will be stretched differently through the prism pair. If you can refocus the beam before the shaping optics, a cylindrical lens combination (achromatic) will be more appropriate.
Poster:mmodena
Posted Date:2014-02-04 12:16:46.72
Hi, I need to shape a circular beam into an elliptical one. As I read, I can use the prism pair in reverse configuration to achieve this. My only concern regards the ar coating: should I purchase an uncoated prism pair? Thank you, Mario Modena
Poster:besembeson
Posted Date:2014-02-07 04:45:32.0
Response from Bweh E at Thorlabs: I think it will be better to use the coated ones, since two of the four surfaces will coincide with the optimal AR coating angle. The other two will be off but based on the reflectivity specifications (see "Reflectivity tab at the following link: http://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=149&pn=PS873-A) you should still be okay.
Poster:christian
Posted Date:2013-12-05 10:01:24.507
I am using using the F810SMA-635 Collimator(with LPM-635-SMA Diode)with a beam aprox. 17mm in diameter. Are there larger prism pairs or other possibilities for transforming to a cylindrical beam?
Poster:cdaly
Posted Date:2013-12-05 02:35:27.0
Response from Chris at Thorlabs: Thank you for your inquiry. I would recommend using a par of cylindrical lenses to manipulate the beam this way. You can use two which are position to share a focal point. If they are lined up the same way, it will expand or reduce the beam in one axis by the ratio of the focal lengths of the lenses.
Poster:bdada
Posted Date:2012-03-15 15:06:00.0
Response from Buki at Thorlabs to sechaniz: As an update, the damage threshold of the uncoated prism is 10 J/cm2, 10 nsec, 10 Hz @ 1064nm.
Poster:bdada
Posted Date:2012-03-15 12:50:00.0
Response from Buki at Thorlabs to sechaniz: Thank you for your feedback. We don't have damage threshold test data for the anamorphic prism pairs, but the damage threshold limit for the coated prisms is determined by the AR coating, which is nominally 100 mJ/cm^2 for a 10 ns pulse or 100W/cm^2 at 1064nm. Based on the information you provided, your beam should have a density of about 12W/cm^2, which is below the damage threshold of the coating. Please contact TechSupport@thorlabs.com if you have any questions.
Poster:sechaniz
Posted Date:2012-03-12 15:41:47.0
Could you please let me know what is the damage threshold of these prisms? In particular, I'd like to use them with an 808 nm laser diode with 1.2 W of power and a beam of 5 x 2 mm. Would this be possible? Thank you.
Poster:bdada
Posted Date:2012-01-27 02:18:00.0
Response from Buki at Thorlabs: Thank you for using our feedback forum. Anamorphic prism pairs can be used in reverse to convert a circular beam into an elliptical one. We do not anticipate any issues. Please contact TechSupport@thorlabs.com if you have additional questions or want to discuss your application further.
Poster:franxm
Posted Date:2012-01-13 14:34:45.0
Any issues if the input and output are reversed (i.e., using the anamorphic prism pair to convert a circular beam into an elliptical one)?
Poster:bdada
Posted Date:2011-03-08 18:09:00.0
Response from Buki: Thank you for your request. We do manufacture custom prisms and we will contact you directly to discuss your application.
Poster:spotnis
Posted Date:2011-03-07 10:26:22.0
Does thorlab manufacture custom prisms with a wide exit aperture? Im looking for a prism pair which has 10-15x expansion and a 20mm exit aperture.
Poster:Thorlabs
Posted Date:2010-10-29 15:37:16.0
Response from Javier at Thorlabs to kjsong: Thank you very much for your feedback. I will discuss adding -A versions of our anamorphic prism pairs with our optics department. I will keep you updated.
Poster:kjsong
Posted Date:2010-10-29 13:41:46.0
I am working with 635nm light. I would like to have PS875-A. But its not listed. It seems odd that there are laser diodes at 400nm and 633nm but no AR coating to cover that range. Its 4 surfaces in an anamorphic prism! That reflects a lot of light!
Poster:Tyler
Posted Date:2008-09-09 17:02:54.0
A response from Tyler at Thorlabs to rieko.verhagen: We dont have damage threshold test data for the anamorphic prism pairs at 1600 nm. However, the damage threshold limit is determined by the AR coating (if present), which is nominally 100 mJ/cm^2 for 10 ns pulse. Does your application require a higher damage threshold?
Poster:rieko.verhagen
Posted Date:2008-09-05 07:50:41.0
Thorlabs, Could you please provide me with the damage threshold for nanosecond pulsed laser operation around 1600nm for the PS872-C anamorphic prism pair? With kind regards, Rieko Verhagen

Unmounted Anamorphic Prism Pairs

These unmounted prism pairs are available uncoated or with an antireflection coating for the 350 - 700 nm (-A), 650 - 1050 nm (-B) or 1050 - 1700 nm (-C) range. The anamorphic expansion (one-dimensional expansion) can be adjusted by changing the angles and the offset between the prisms. Please see the Beam Expansion tab for details.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
PS870 Support Documentation
PS870N-SF11 Unmounted Anamorphic Prism Pair, Uncoated
$126.00
Today
PS873-A Support Documentation
PS873-ACustomer Inspired!N-KZFS8 Unmounted Anamorphic Prism Pair, ARC: 350 - 700 nm
$159.00
Today
PS871-B Support Documentation
PS871-BN-SF11 Unmounted Anamorphic Prism Pair, AR Coating: 650 - 1050 nm
$152.00
Today
PS872-C Support Documentation
PS872-CN-SF11 Unmounted Anamorphic Prism Pair, AR Coating: 1050 - 1700 nm
$159.00
Today

Mounted Anamorphic Prism Pairs, AR Coated: 350 - 700 nm

Item # Anamorphic
Magnificationa
Input Offset, Lb
(mm)
PS875-A 2.0 4.7
PS879-A 3.0 5.85
PS883-A 4.0 5.81
  • Measured at 405 nm.
  • Refer to Drawing Above. Please note that the output beam will not exit at the center of the aperture.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
PS875-A Support Documentation
PS875-ACustomer Inspired!N-KZFS8 Mounted Prism Pair, ARC: 350 - 700 nm, Mag: 2.0
$360.00
Today
PS879-A Support Documentation
PS879-ACustomer Inspired!N-KZFS8 Mounted Prism Pair, ARC: 350 - 700 nm, Mag: 3.0
$360.00
Today
PS883-A Support Documentation
PS883-ACustomer Inspired!N-KZFS8 Mounted Prism Pair, ARC: 350 - 700 nm, Mag: 4.0
$360.00
Today

Mounted Anamorphic Prism Pairs, AR Coated: 650 - 1050 nm

Item # Anamorphic
Magnificationa
Input Offset, Lb
(mm)
PS875-B 2.0 3.7
PS877-B 2.5 5.15
PS879-B 3.0 5.43
PS880-B 3.2 5.63
PS881-B 3.5 6.0
PS883-B 4.0 6.06
  • Measured at at 670 nm.
  • Refer to Drawing Above. Please note that the output beam will not exit at the center of the aperture.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
PS875-B Support Documentation
PS875-BN-SF11 Mounted Prism Pair, ARC: 650 - 1050 nm, Mag: 2.0
$360.00
Today
PS877-B Support Documentation
PS877-BN-SF11 Mounted Prism Pair, ARC: 650 - 1050 nm, Mag: 2.5
$360.00
Today
PS879-B Support Documentation
PS879-BN-SF11 Mounted Prism Pair, ARC: 650 - 1050 nm, Mag: 3.0
$360.00
Today
PS880-B Support Documentation
PS880-BN-SF11 Mounted Prism Pair, ARC: 650 - 1050 nm, Mag: 3.2
$360.00
Today
PS881-B Support Documentation
PS881-BN-SF11 Mounted Prism Pair, ARC: 650 - 1050 nm, Mag: 3.5
$360.00
Today
PS883-B Support Documentation
PS883-BN-SF11 Mounted Prism Pair, ARC: 650 - 1050 nm, Mag: 4.0
$360.00
Today

Mounted Anamorphic Prism Pairs, AR Coated: 1050 - 1700 nm

Item # Anamorphic
Magnificationa
Input Offset,
L (mm)b
PS875-C 2.0 3.37
PS879-C 3.0 5.43
PS883-C 4.0 6.06
  • Measured at at 670 nm.
  • Refer to Drawing Above. Please note that the output beam will not exit at the center of the aperture.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
PS875-C Support Documentation
PS875-CN-SF11 Mounted Prism Pair, ARC: 1050 - 1700 nm, Mag: 2.0
$360.00
Today
PS879-C Support Documentation
PS879-CN-SF11 Mounted Prism Pair, ARC: 1050 - 1700 nm, Mag: 3.0
$360.00
Today
PS883-C Support Documentation
PS883-CN-SF11 Mounted Prism Pair, ARC: 1050 - 1700 nm, Mag: 4.0
$360.00
Today
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