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Telecom Zero-Order Wave Plates


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Telecom Zero-Order Wave Plates

Common Specifications
MaterialCrystalline Quartz
Size5.0 mm x 5.0 mm
Retardance Accuracy (Typical)<λ/300
Transmitted Wavefront Errorλ/10
Surface Quality20-10 Scratch-Dig
Parallelism10 arcsec
Damage Threshold (Typical)2 MW/cm2 (CW)
2 J/cm2 (10 ns Pulse)
Reflectance<0.25%
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.

Features

  • Designed for Use with 1550 nm Lasers
  • Compact Size
    • 5.0 mm x 5.0 mm x 137 µm (Quarter-Wave Plate)
    • 5.0 mm x 5.0 mm x 91 µm (Half-Wave Plate)
  • Ideal for Compact OEM Systems

Thorlabs' Telecom Wave Plates are compact, zero-order wave plates specifically designed to meet the demanding requirements of WDM component designers using 1550 nm light. The half-wave plate can be used to rotate the polarization state, while the quarter-wave plate can be used to convert linearly polarized light into a circular (elliptical) polarization state and vice versa.

The true zero-order nature of these wave plates ensures the best possible angle, temperature, and wavelength performance. Their small size (5.0 mm x 5.0 mm) makes them ideal for reducing the overall package size of your designs. The true zero-order half-wave plates are 91 μm thick, while the zero-order quarter-wave plates are 137 µm thick. Upon request, Thorlabs can provide these with custom sizes and center wavelengths; please contact Tech Support for more information..

For further information on using and selecting a wave plate, please see our Selection Guide tab.

Telecom Waveplates Slow Axis Drawing
Wave Plate Selection Guide
AchromaticSuperachromaticQuartz Zero-Order Half-WaveQuartz Zero-Order Quarter-WavePolymer Zero-OrderMulti-OrderDual WavelengthTelecomPolarization Optics

Choosing a Wave Plate

Thorlabs offers achromatic, superachromatic, zero-order (both unmounted wave plates and mounted wave plates), and multi-order wave plates (single wavelength and dual wavelength) with either λ/4 or λ/2 phase shift.

Achromatic Wave Plates provide phase retardance that is relatively independent of wavelength over a wide spectral range, and Superachromatic Wave Plates provide phase retardance almost entirely independent of wavelength over a much wider range than achromatic wave plates. In contrast, zero-order and multi-order wave plates provide a phase shift that is wavelength dependent. Our achromatic wave plates are available with four AR coatings: 260 - 410 nm, 400 - 800 nm, 690 - 1200 nm, and 1100 - 2000 nm. In contrast, our superachromatic wave plates have AR coatings for 600 - 2700 nm.

Round Zero-Order Wave Plate Comparison
MaterialQuartzLCP
SizesØ1/2" and Ø1"Ø1" and Ø2"
MountedYesOnly Ø2" Versions
Retardances Available1/4 λ and 1/2 λ1/4 λ and 1/2 λ
Retardance Accuracy<λ/300<λ/100
Surface Quality20-10 Scratch-Dig60-40 Scratch-Dig
CoatingV CoatBroadband AR
Coating Reflectance
(per Surface)
0.25%0.5% Average Over Specified Coating Range

Zero-order waveplates are designed such that the phase shift created is exactly one quarter or one half of a wave. They offer substantially lower dependence on temperature and wavelength than multi-order wave plates. Our Zero-Order Quartz Half-Wave and Quarter-Wave Plates are composed of two wave plates stacked together with the fast axis of one aligned to the slow axis of the other to achieve zero-order performance. Thorlabs' zero-order wave plates are available for a number of discrete wavelengths ranging from 266 nm to 2020 nm. Our Polymer Zero-Order Wave Plates consist of a thin layer of liquid crystal polymer retarding material sandwiched between two glass plates and are available at discrete wavelengths between 405 nm and 1053 nm. Our quartz zero-order wave plates provide better retardance accuracy and lower reflectance (see table), while our LCP zero-order wave plates produce a smaller decrease in retardance at larger AOIs. In addition, Thorlabs also offers unmounted true Zero-Order Telecom Wave Plates for WDM applications.

Multi-Order Wave Plates are made such that the retardance of a light path will undergo a certain number of full wavelength shifts (also referred to as the order, or m) in addition to the fractional design retardance. Compared to their zero-order counterparts, the retardance of multi-order wave plates is more sensitive to wavelength and temperature changes. Multi-order wave plates are, however, a more economical solution for many applications where increased sensitivities are not an issue. Our multi-order wave plates are available for a number of discrete wavelengths ranging from 266 nm to 1550 nm. Thorlabs also offers Dual-Wavelength Multi-Order Wave Plates designed for use at both 532 nm and 1064 nm.

 

Operating Principle of Wave Plates

Optical wave plates are constructed from birefringent material that introduces a phase difference between the fast and slow principal axes of the wave plate. The birefringent properties of the material create a difference in refractive index between the two axes. This in return creates a difference in the velocity between the two orthogonal components. The fast principal axis of the wave plate has a lower refractive index resulting in faster wave velocity. The slow axis has a higher refractive index, resulting in slower velocity. The actual phase shift created depends on the properties of the material, the thickness of the wave plate and the wavelength of the signal, and can be described as:

Phase Shift

where n1 is the refractive index of the principal plane, n2 is the refractive index of the orthogonal plane, and d is the thickness of the wave plate.

 

Using a Wave Plate

Wave plates are typically available with a retardance of λ/4 or λ/2, meaning that a phase shift of quarter of a wavelength or half a wavelength (respectively) is created.

Half-Wave

beam diagram
Half-Wave Plate Diagram

As described above, a wave plate has two principal axes: fast and slow. Each axis has a different refractive index and, therefore, a different wave velocity. When a linearly polarized beam is incident on a half-wave plate, and the polarization of this beam does not coincide with one of these axes, the output polarization will be linear and rotated with respect to the polarization of the input beam (see image at left). When applying a circularly polarized beam, a clockwise (counterclockwise) circular polarization will transform into a counter-clockwise (clockwise) circular polarization.

Half-wave (λ/2) plates are typically used as polarization rotators. Mounted on a rotation mount, a λ/2 wave plate can be used as a continuously adjustable polarization rotator, as shown below. Additionally, when used in conjunction with a Polarizing Beamsplitter a λ/2 wave plate can be used as a variable ratio beamsplitter.

The angle between the output polarization and the input polarization will be twice the angle between the input polarization and the wave plate’s axis (Θ), see diagram below left. When the polarization of the input beam is directed along one of the axes of the wave plate, the polarization direction will remain unchanged.

Half-Wave Plate and Rotation Mount
Click to Enlarge

Half-Wave Plate Mounted in RSP1X15 Rotation Mount

Quarter-Wave

beam diagram

A quarter-wave plate is designed such that the phase shift created between the fast and slow axes is a quarter wavelength (λ/4) or a multiple of λ/4. When applying a linearly polarized beam with the polarization plane aligned at 45° to the wave plate’s principal plane, the output beam will be circularly polarized (see image at left). Likewise, when applying a circularly polarized beam to a λ/4 wave plate the output beam will be linearly polarized. Quarter wave plates are used in Optical Isolators, optical pumps, and EO modulators.

Damage Threshold Specifications
Damage Specification TypeDamage Threshold
Pulsed2 J/cm2  (10 ns)
CW 2 MW/cm2

Damage Threshold Data for Thorlabs' Telecom Zero Order Waveplates

The specifications to the right are measured data for Thorlabs' telecom zero order waveplates. Damage threshold specifications are constant for all telecom zero order waveplates.

 

Laser Induced Damage Threshold Tutorial

This 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 specifications. A standard 1-on-1 testing regime is performed to test the damage threshold.

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 a set duration of time (CW) or number of pulses (prf 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 LocationsLocations with DamageLocations Without Damage
1.50 J/cm210010
1.75 J/cm210010
2.00 J/cm210010
2.25 J/cm21019
3.00 J/cm21019
5.00 J/cm21091

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 it is only representative of one coating run and that Thorlabs' specified damage thresholds 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. Additionally, when pulse lengths are between 1 ns and 1 µs, LIDT can occur either because of absorption or a dielectric breakdown (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 large 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. Linear power density of your beam (total power divided by 1/e2 spot size)
  3. Beam diameter of your beam (1/e2)
  4. Approximate intensity profile of your beam (e.g., Gaussian)

The power density of your beam should be calculated in terms of W/cm. The graph to the right shows why the linear power density provides the best metric for long pulse and CW sources. Under these conditions, linear power density scales independently of spot size; 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 consider hotspots in the beam or other nonuniform 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). 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 pulse lengths that our specified LIDT values are relevant for.

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 Durationt < 10-9 s10-9 < t < 10-7 s10-7 < t < 10-4 st > 10-4 s
Damage MechanismAvalanche IonizationDielectric BreakdownDielectric Breakdown or ThermalThermal
Relevant Damage SpecificationN/APulsedPulsed and CWCW

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 the energy density provides the best metric for short pulse sources. Under these conditions, energy density scales independently of spot size, 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 power 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 (1997).
[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).

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Posted Comments:
Poster: bdada
Posted Date: 2012-01-30 18:22:00.0
Response from Buki at Thorlabs: Thank you for using our feedback forum. These Telecom Zero-Order Waveplates are designed for compact OEM systems, so we do not offer them mounted. Toward the end of the "Overview" tab, we mention various mounted waveplates that we offer. Please review the product pages linked to see if one may be suitable for your application. We have contacted you to discuss this further.
Poster: mathieu.perrin
Posted Date: 2012-01-30 10:55:17.0
Which is the preferred optical mount offered by Thorlabs to mount those small waveplates? Regards, Mathieu.
Poster: bdada
Posted Date: 2011-09-21 14:57:00.0
Response from Buki at Thorlabs: Thank you for your inquiry. We have contacted you to determine if you are looking for the retardance or reflectivity values at a different angle of incidence. If you are looking for the accuracy of the retardance with respect to the angle at which the optical axis is aligned to the light polarization axis, we specify a retardance accuracy of
Poster: goetz
Posted Date: 2011-09-02 11:52:45.0
Can I get information on the angle sensitivity of the WPQ501? I also would be interested in a 10 mm x 10 mm quarter wave plate. Thank you, Peter Goetz
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