Infrasil® Textured Broadband Antireflective Windows
- Antireflective Performance Provided by Subwavelength Surface Structures
- <0.25% Average Reflectance from 1000 to 1700 nm
- Ideal for Applications Requiring Long-Term Beam Stability
Ø1" Textured Broadband AR Window
Lower Reflectance Over a Broad Wavelength Range*
Higher Laser Damage Threshold*
Lower Angular Sensitivity*
*When Compared to Thorlabs' -C Broadband Antireflective (BBAR) Coating
(See the Comparison Tab for Details)
Ø1/2" Textured Broadband AR Window
|Wavelength Range||1000 - 1700 nm|
|Damage Thresholdb||>30 J/cm2 at 1064 nm,
10 ns, 10 Hz, Ø0.23 mm
|Ravg < 0.25%|
|Tabs ≥ 98.0%|
(Click for Graph)
Click to Enlarge
An SEM image showing a top-view of the nanostructured window surface.
|Flat Window Selection Guide|
|Wavelength Range||Substrate Material|
|180 nm - 8.0 μm||Calcium Fluoride (CaF2)|
|185 nm - 2.1 μm||UV Fused Silica|
|200 nm - 5.0 μm||Sapphire|
|200 nm - 6.0 μm||Magnesium Fluoride (MgF2)|
|250 nm - 1.6 µm||UV Fused Silica, for 45° AOI|
|250 nm - 26 µm||Potassium Bromide (KBr)|
|300 nm - 3 µm||Infrasil®|
|350 nm - 2.0 μm||N-BK7|
|400 nm - 1.1 µm||UV Fused Silica, Textured Antireflective Surface|
|600 nm - 16 µm||Zinc Selenide (ZnSe)|
|1 - 1.7 µm||Infrasil®,
Textured Antireflective Surface
|1.2 - 8.0 μm||Silicon (Si)|
|1.9 - 16 μm||Germanium (Ge)|
|2 - 5 μm||Barium Fluoride (BaF2)|
|V-Coated Laser Windows|
- Designed for Use from 1000 to 1700 nm
- <0.25% Average Reflectance Per Surface
- ≥98.0% Absolute Transmission
- Ideal for NIR Applications Requiring Long-Term Beam Stability
- High Resistance to Laser-Induced Damage
Thorlabs' Infrasil®† Textured Antireflective Window is a high-performance window with a nanostructured surface, resulting in ≥98% transmission over a broad wavelength range (1000 - 1700 nm). By including a structured surface instead of a traditional thin-film coating, this textured window offers lower reflectance (<0.25% per surface) and higher laser damage resistance (>30 J/cm2), as well as long-term stability. Please see the Comparison tab for a detailed comparison of our T2 textured surface to our broadband antireflection (BBAR) coatings. A Ø1", 1.0 mm thick, Infrasil textured window is available from stock; please click the "Contact Me" button below to discuss custom requests.
In contrast to AR coatings where thin layers are deposited on the substrate surface, this textured window is created by removing material from the bulk substrate using our proprietary process, which has been optimized to fabricate subwavelength structures. Texturing the window surface results in an effective refractive index layer that suppresses reflected light over a broad wavelength range; an SEM image of the structured window surface is shown to the right.
Thorlabs also offers a UVFS textured window with similar performance over the 400 to 1100 nm wavelength range. We have a selection of High Precision Windows fabricated from various substrate materials for use in a large variety of laser and industrial applications. Additionally, we offer laser windows and wedged laser windows, which have AR V-coatings centered around commonly used laser wavelengths, as well as Brewster windows, which are used to eliminate p-polarized reflections.
The nanostructures, which are on both sides of the window, may be adversely affected by contact with mounting surfaces or retaining rings, causing localized performance degradation. To minimize the impacted areas, we recommend mounting these windows in an SM1-threaded mount, such as the LMR1(/M) Fixed Lens Mount, with an SM1LTRR Stress-Free Retaining Ring.
Our engineers and expertise are here for you!
Thorlabs Spectral Works
If you are not sure whether our catalog textured windows meet your needs, we invite you to contact us to discuss your specific application, including custom or OEM requirements you may have.
Just press the button, and we'll get back to you within the next business day.
Handling Precautions and Cleaning
Thorlabs' Textured Window could be contaminated or damaged by moisture, fingerprints, aerosols, or contact with any abrasive material. This window should only be handled when necessary and always held by the sides using our TZ2 or TZ3 tweezers. Latex gloves or a similar protective covering should be worn to prevent oil from fingers from reaching the structured surface.
If the surface is comtaminated, the window may be cleaned by:
- Blowing off dust with clean air or nitrogen
- Rinsing with solvents, such as isopropyl alcohol, followed by clean air or nitrogen blow-drying
- Immersing in a basic solution (a mix of ammonium hydroxide and hydrogen peroxide) and/or an acid solution (a mix of hydrogen chloride and hydrogen peroxide) followed by clean air or nitrogen blow-drying
Standard cleaning methods will result in further contamination and thus should be avoided.
†Infrasil is a registered trademark of Heraeus Quarzglas.
|Wavelength Range||1000 - 1700 nm|
|Diameter||1" (25.4 mm)|
|Diameter Tolerance||+0.0 / -0.2 mm|
|Thickness Tolerance||±0.1 mm|
|Clear Aperture||≥Ø21.59 mm|
|Surface Quality||10-5 Scratch-Dig|
|Transmitted Wavefont Error||<λ/10 at 633 nm|
|Damage Threshold||>30 J/cm2 at 1064 nm, 10 ns, 10 Hz, Ø0.23 mm|
|Reflectance Over Wavelength Rangeb||Ravg < 0.25%|
|Transmission Over Wavelength Rangec||Tabs ≥ 98.0%|
|Transmission Data (Click for Graph)||
|Coating or Surface
Designation (Item # Suffix)
|T2||1000 - 1700 nm||<0.25%|
|-C||1050 - 1700 nm||<0.5%|
Thorlabs' WGN101T2 Textured Window is currently available with our T2 textured surface, which offers antireflective performance over a broad 1 to 1.7 µm wavelength range. The graphs below compare the performance of the T2 textured surface to the 1050 - 1700 nm (designated as -C) broadband antireflective (BBAR) coating.
The average reflectance of the T2 surface and BBAR coatings are listed in the table to the right. Each provides good performance for angles of incidence (AOI) between 0° and 30° and a numerical aperture (NA) of 0.5.
The performance plot to the right shows a comparison of the reflectance of Thorlabs' -C BBAR coating and the T2 textured surface. The blue arrow indicates the specified 1050 - 1700 nm wavelength range for the -C BBAR coating. The T2 surface wavelength range of 1000 nm - 1700 nm is indicated by the red arrow.
Angle of Incidence (AOI) and Polarization
Each performance plot shows the s- and p-polarized reflectance at several AOI for the 1.0 mm thick Infrasil T2 textured surface (Item # WGN101T2) or -C coating when applied to a 1.0 mm thick UVFS window (Item # WG41010-C). With its low angular sensitivity, the T2 surface reflectance is expected to stay relatively low over a large range of angles for both s- and p-polarized light. In contrast, the s-polarized reflectance values for the -C coating are expected to rapidly rise with increasing AOI, while the p-polarized reflectance should show a slight decrease before increasing. The blue-shaded region indicates the specified wavelength range of each surface or coating.
|Damage Threshold Specifications|
|Item #||Damage Threshold|
|WGN101T2||>30 J/cm2 at 1064 nm, 10 ns, 10 Hz, Ø0.23 mm|
Damage Threshold Data for Thorlabs' Textured Antireflective Window
The specification to the right is measured data for Thorlabs' WGN101T2 textured window.
To demonstrate improved resistance to laser-induced damage, LIDT testing was performed on the WGN101T2 textured window for fluences up to 71 J/cm2. Damage sites, which appear red in the exposure histogram below, are not observed on the textured window until exposure to a fluence of 71 J/cm2. For a detailed description of the LIDT testing method, please see the Testing Method section of the Laser Induced Damage Threshold Tutorial below.
|WGN101T2 LIDT Testing Dataa|
|Fluence||# of Tested
Click to Enlarge
Exposure Histogram for LIDT Testing on the WGN101T2 Textured Window Measurements Beam Parameters: 1064 nm, 10 ns, 10 Hz, Ø0.23 mm
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.
Thorlabs' LIDT testing is done in compliance with ISO/DIS 11254 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.
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.
|Example Test Data|
|Fluence||# of Tested Locations||Locations with Damage||Locations Without Damage|
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) . 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.
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:
- Wavelength of your laser
- Beam diameter of your beam (1/e2)
- Approximate intensity profile of your beam (e.g., Gaussian)
- 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):
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.
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 . 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:
- Wavelength of your laser
- Energy density of your beam (total energy divided by 1/e2 area)
- Pulse length of your laser
- Pulse repetition frequency (prf) of your laser
- Beam diameter of your laser (1/e2 )
- 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 . 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):
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 . 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:
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.
 R. M. Wood, Optics and Laser Tech. 29, 517 (1998).
 Roger M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, Philadelphia, PA, 2003).
 C. W. Carr et al., Phys. Rev. Lett. 91, 127402 (2003).
 N. Bloembergen, Appl. Opt. 12, 661 (1973).
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