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Optical Coatings


Optical Coatings
  • State-of-the-Art, In-House Coating Lab
  • Broad Range of Coating Capabilites on a Wide Variety of Substrates


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Close-Up of the E-Beam Chamber
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Interior of an E-Beam Deposition Chamber
Thorlabs OEM Brochure

Thorlabs' Coating Capabilities

Thorlabs' state-of-the-art, in-house, optical coating department provides us with coating capabilities ranging from metal coatings and antireflective coatings to cutting edge Ion Beam Sputtered (IBS) and Plasma Assisted coatings. This full-scale facility not only allows us to produce large numbers of our catalog optics in house but also expands our ability to manufacture custom-coated optics to suit a variety of customer needs.

Coating Design

Coating Design
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Layered Coating Stack

The spectral performance and other key characteristics of optical thin films are determined by the structure and number of layers in the coating, the refractive indices of the materials used, and the optical properties of the substrate.

The structure of most coatings resembles a series of discrete alternating layers of high index and low index materials. Different arrangements of stack structure result in different types of coatings (e.g., Bandpass vs. Edgepass vs. BBAR). Fine tuning of layer thicknesses and refractive indices is done to optimize performance characteristics in the wavelength range of interest. Thorlabs has a selection of thin film modeling tools to design, characterize, and optimize many aspects of an individual coating's performance.

Cleaning

The first and one of the most critical steps of our process is cleaning uncoated substrates with an automated ultrasonic clean line. Using a series of ultrasonic solvent and detergent baths, each step of the cleaning process removes different types of contamination from the surfaces of the substrate. This ensures surface contamination does not interfere with adhesion of coatings to the substrate.

Fully Automated Cleaning System
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Fully Automated Optical Cleaning System
Optics in Cleaning Carrier
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Optics After Cleaning

E-Beam Deposition

Thorlabs' coating facility currently operates four fully automated Electron Beam (E-Beam) deposition systems. These systems use an electron beam source to evaporate a selection of materials such as transition metal oxides (e.g., TiO2, Ta2O5, HfO2, Nb2O5, ZrO2), metal halides (MgF2, YF3), or SiO2. This type of process must be done at elevated temperatures (200 - 250 °C) to achieve good adhesion to the substrate and acceptable material properties in the final coating.

 

Ion-Assisted E-Beam Deposition

Ion-Beam Assisted Deposition (IAD) uses the same E-beam method to evaporate coating materials but with the addition of an ion source to promote nucleation and growth of materials at lower temperatures (20 - 100 °C). The ion source allows temperature-sensitive substrates to be coated. This process also results in a denser coating that is less sensitive to spectral shifting in both humid and dry environmental conditions.

IBS Deposition

Our Ion Beam Sputtering (IBS) deposition chamber is the most recent addition to our line-up of coating tools. This process uses a high energy, radio frequency, plasma source to sputter coating materials and deposit them on substrates while another RF ion source (Assist source) provides IAD function during deposition. The sputtering mechanism can be characterized as momentum transfer between ionized gas molecules from the ion source and the atoms of the target material. This is analogous to a cue ball breaking a rack of billiard balls, only on a molecular scale and with several more balls in play.

Advantages of IBS

  • Better Process Control
  • Wider Selection of Coating Designs
  • Improved Surface Quality and Less Scatter
  • Reduced Spectral Shifting
  • Thicker Coating in a Single Cycle
Coated Retroreflectors in Tool
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Coated Retroreflectors in Tool

Metrology

Thorlabs uses a selection of research-grade spectroscopy instruments to characterize coating performance from the UV to the Far Infrared. Varian Cary 5000 and PE Lambda 950 spectrophotometers are used to characterize the spectral performance of our coatings in the UV-VIS-NIR ranges and an Olis PE 983 IR spectrophotometer is used for infrared coatings (2 - 55.5 µm). In addition to the spectroscopy tools, we also use a variety of laser and laser diode sources, power meters, detectors, and polarimeters to test the performance of our optics. We build custom setups to test both catalog and OEM parts to ensure every optic we offer performs well within the specified range. All of our metrology instruments are calibrated regularly per ISO 9001:2015 standard.

Laser Line/Bandpass Filters

Laser Line and Bandpass filters transmit light in a narrow, well-defined spectral region while rejecting other unwanted radiation. This type of filter displays very high transmission in the bandpass region and blocks a limited spectral range of light on either side of the bandpass region. To compensate for this deficiency, an additional blocking component is added, which is either an all-dielectric or a metal-dielectric depending on the requirements of the filter. Although this additional blocking component eliminates any unwanted out-of-band radiation, it also reduces the filter's overall transmission throughput.

These coatings are formed by vacuum deposition coating techniques and consist of two reflecting stacks, separated by an even-order spacer layer. These reflecting stacks are constructed from alternating layers of high and low refractive index materials, which can have a reflectance in excess of 99.99%. By varying the thickness of the spacer layer and/or the number of reflecting layers, the central wavelength and bandwidth of the filter can be altered.

Edgepass Filters

Edgepass filters are very useful for isolating specific spectral regions. Longpass filters transmit wavelengths longer than the cutoff wavelenght and block wavelengths shorter than the cutoff wavelength. Shortpass filters block wavelengths longer than the cutoff wavelength and transmit those shorter than the cutoff wavelength.

All Thorlabs edgepass filters are constructed of durable dielectric coatings and will withstand the normal cleaning and handling associated with any high-quality optical component. Their film construction is essentially a modified quarter-wave stack, using interference effects rather than absorption to isolate their spectral bands.

Dichroic Beamsplitters

Dichroic Beamsplitters are used as beam directors at 45° and are either longpass or shortpass. The longpass variety reflects >90% of the incident light below the design wavelength and transmits >90% of the incident light above the design wavelength. The shortpass variety transmits below the design wavelength, and reflects above the design wavelength. Dichroic beamsplitters are used in many applications, the most common one being fluorescence microscopy.

The dielectric coating on dichroic beamsplitters is the source of their functionality. The alternating layers in the coating are designed to cause constructive interference for those wavelengths to be transmitted and destructive interference for those wavelengths to be reflected. The thickness of the coating and the refractive index of the materials in the layers determine the design wavelength for a given beamsplitter.

Notch Filters

Notch filters, also commonly referred to as band-stop or band-rejection filters, are designed to transmit most wavelengths but attenuate light within a specific wavelength range (the stop band) to a very low level. They are functionally the inverse of bandpass filters and are made in the same way.

Neutral Density Filters

Neutral Density (ND) filters attenuate all wavelengths within a range by a certain factor to prevent damage to detecting equipment. Fixed ND filters attenuate the spectra by a fixed amount. Variable ND filters have stepped films at discrete locations to allow for various attenuation depending on the application. Continuous ND filters have a film gradient across the entire filter, which allows for a continuous range of attenuation. Thorlabs offers a selection of both linear and circular variable and continuous ND filters.

Antireflective (AR) coatings are hard refractory-oxide coatings that minimize surface reflections within specified wavelength ranges when applied to the surface of optical components. Without AR coating, 4% of the light is lost at each optical surface due to reflections. For example, if three uncoated lenses are being used in series, this 4% loss occurs at each of the six optical surfaces. This results in a total loss of 21.7%. If three AR-coated lenses with a "B" coating (Ravg <0.5% per surface) are used instead, the total loss of incident light due to surface reflections is <3%. The use of AR-coated optics improves transmission from 78.3% to greater than 97% in this case. Please note that the 4% loss at the interfaces of uncoated optics is an approximate value that varies greatly with material and angle of incidence (AOI). Please note that the color of the lens does not correlate to the lens’ specifications. The color of each AR coating may vary from batch to batch and is not an indicator of performance.

The AR Coating Range graph below shows the specified wavelength range of Thorlabs' in-house AR coatings. Click on the bars in the graph below to view the performance plot for each coating.


AR Coating Comparison
G AR Coating F AR Coating E3 AR Coating E2 AR Coating E4 AR Coating E AR Coating D AR Coating C AR Coating B AR Coating AB AR Coating A AR Coating UV AR Coating

Broadband antireflective (BBAR) coatings consist of multiple layers, alternating between a high index material and a low index material. The layers are deposited on the substrate via electron-beam deposition. The thickness of the layers is optimized, using modeling software, to produce destructive interference between reflected waves and constructive interference between transmitted waves. This results in an optic that has enhanced performance within a specified wavelength band as well as minimal internal reflections (ghosting). Thorlabs' BBAR coatings provide good performance for angles of incidence between 0° and 30° and a numerical aperture (NA) of 0.5. Thorlabs currently offers BBAR coatings designed to maximize performance within 8 different wavelength ranges.

V-coatings are multilayer, dielectric, thin-film, AR coatings that are designed to minimize reflectance over a short wavelength range. Surface reflectance rises rapidly on either side of this minimum, which gives the reflectance curve a "V" shape. Compared to the broadband AR coatings, V-coatings achieve lower reflectance over a narrower bandwidth when used within their design AOI range. See the graph to the right for an example of the reflectance of a 633 nm V-coat designed for 0° AOI at various angles. We offer a variety of different V-coatings; see the table below for more information.

The tables below give the specifications for Thorlabs' in-house antireflection coatings, which are deposited on the surfaces of many optics in our catalog. However, we also offer optics that are coated by external vendors. As such, the specifications for some of our antireflection coated optics may be slightly different than the specifications given on this page. The AR coating specifications for any individual item are always included in that item's web presentation.

Broadband Antireflective Coating Specifications
Coating Code Wavelength Range Reflectancea Performance
Plotb
Coating
Variationc
UV 245 - 400 nmd Ravg < 0.5% Unavailable
A 350 - 700 nm Ravg < 0.5% Icon
Raw Data
AB 400 - 1100 nm Ravg < 1.0% Unavailable
B 650 - 1050 nm Ravg < 0.5% Icon
Raw Data
C 1050 - 1700 nme Ravg < 0.5% Icon
Raw Data
D 1.65 - 3.0 µm Ravg < 1.0% Unavailable
Ef,g 2 - 5 µm Ravg < 1.25% Unavailable
E1g 2 - 5 µm Ravg < 1.50%
Rabs < 3.0%
E4 2 - 13 µm Ravg < 3.5%
Rabs < 6%

Raw Data
Unavailable
E2 4.5 - 7.5 µm Ravg < 1.0%
Rabs < 2.0%
Unavailable
E3h 7 - 12 µm Ravg < 1.0%
Rabs < 2.0%
Unavailable
F 8 - 12 µm Ravg < 1.5% Unavailable
Gh 7 - 12 µm Ravg < 1.0% Unavailable
  • To calculate Ravg, the reflectance is measured over the specified wavelength range and then averaged.
  • The shaded region in the plots represents the specified wavelength range for optimum performance.
  • Optical coatings vary from run to run. The specifications provided throughout our website are true for all coating runs. However, these plots give you some idea of the variation that does occur.
  • The UV coating wavelength range specification was recently updated from 290 - 370 nm to 245 - 400 nm. All optics in stock currently have a UV coating with a wavelength range of 245 - 400 nm. However, we are in the process of updating our documentation, and so some individual optics may still be presented with the old wavelength range on our website.
  • The C coating wavelength range specification was recently updated from 1050 - 1620 nm to 1050 - 1700 nm. All optics in stock currently have a C coating with a wavelength range of 1050 - 1700 nm. However, we are in the process of updating our documentation, and so some individual optics may still be presented with the old wavelength range on our website.
  • Manufacturing processes of E-coated optics have recently changed. Physical appearance (e.g., color) of these optics may vary based on factors including materials and processes. The specified performance will be achieved regardless of color variations.
  • The E and E1 coatings offer similar performance, but the -E1 coating guarantees an absolute reflectance of <3.0% over the specified wavelength range.
  • The G and E3 coatings offer similar performance, but the -E3 coating guarantees an absolute reflectance of <2.0% over the specified wavelength range.
Narrowband Antireflective (V-) Coating Specifications
Coating Code Design Wavelength Reflectance
per Surfacea
Performance
Plot
405 405 nm <0.25% Icon
Raw Data
532 532 nm <0.25% Icon
Raw Data
633 633 nm <0.25%
780 780 nm <0.25%
1064 1064 nm <0.25% Icon
Raw Data
YAG 532/1064 nm <0.25%
  • The reflectance is measured at the design wavelength.
AOI Dependence
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Dependence of Reflectance on Angle of Incidence
for a 633 nm V-Coat Designed for 0° AOI

Table of Contents

The tables below give specifications for our broadband and narrowband high-reflectance (HR) coatings. Thorlabs offers dielectric and metallic broadband coatings, as well as dielectric narrowband coatings for laser line applications. We also offer specialty ultrafast mirrors for femtosecond pulsed lasers.

Dielectric HR coatings, available in broadband or narrowband designs, are hard, refractory, oxide coatings that maximize surface reflections within a specific wavelength range and angle of incidence. The coating consists of alternating layers of high and low index materials. The layer's thickness is optimized, using computer models, to produce constructive interference for reflected waves and destructive interference for all other wavelengths. The reflectance of the surface is improved greatly by the addition of an HR coating; however, its performance is dependent on the angle of incidence (AOI). At high AOIs, the reflection band shifts to shorter wavelengths and performs differently for S and P polarizations.

Broadband HR Coatings
Thorlabs currently offers nine different broadband HR coatings optimized for various performance parameters. The graph below shows the specified wavelength range of Thorlabs' in-house broadband HR coatings. Click on the bars in the graph below to view the performance plot for each coating. Click here for a raw data file that compares all of our broadband HR Coatings.

HR Coating Comparison
E01 HR Coating E02 HR Coating E03 HR Coating E04 HR Coating UV Enhanced Aluminum Coating Protected Aluminum Coating Protected Silver Coating Ultrafast-Enhanced Silver Coating Protected Gold Coating MIR-Enhanced Gold Coating Unprotected Gold Coating

The E01, E02, E03, and E04 dielectric HR coatings offer high reflectance over broad wavelength ranges. Our UV-Enhanced Aluminum coating has an overcoat of MgF2 to increase the average reflectance in the UV portion of the spectrum. The Protected Aluminum coating is an inexpensive solution and has an overcoat of SiO2 to make the aluminum coating suitable for laboratory and industrial use. Of the metallic coatings, the Protected Silver coating has the highest reflectance in the visible spectrum to prevent oxidization, the silver surface is protected with an SiO2 overcoat. The Ultrafast-Enhanced Silver coating is manufactured such that it retains a low group delay dispersion. Three gold coating options are offered: protected, MIR enhanced, and unprotected. The Protected Gold coating retains a high reflectance down to 800 nm, while the MIR enhanced gold coating is optimized to reduce loses in the MIR that are commonly found in gold mirrors. Each coating in protected by an overcoat that also makes the mirror easy to clean. The Unprotected Gold coating offers higher reflectance than the protected gold coating, but is slightly more delicate.


Broadband HR Coating Specifications
Coating Namea Wavelength Range Average Reflectanceb Graphs Pulsed Laser Damage Threshold for
UV Fused Silicac
CW Laser Damage Threshold for UV Fused Silicad
E01 350 - 400 nm >99% info 1 J/cm2 (355 nm, 10 ns, 10 Hz, Ø0.373 mm) -
E02 400 - 750 nm >99%
info
0.25 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.803 mm) 550 W/cm (532 nm, Ø1.000 mm)
E03 750 - 1100 nm >99% info 0.205 J/cm2 (800 nm, 99 fs, 1 kHz, Ø0.166 mm)
0.5 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø0.433 mm)
1 J/cm2 (810 nm, 10 ns, 10 Hz, Ø0.133 mm) 
10 kW/cm (1070 nm, Ø0.971 mm)
E04 1280 - 1600 nm >99% info 2.5 J/cm2 (1542 nm, 10 ns, 10 Hz, Ø0.181 mm) 350 W/cm (1540 nm, Ø1.030 mm)
UV-Enhanced Aluminum
(-F01)
250 - 450 nm >90% info 0.25 J/cm2 (266 nm, 10 ns, 10 Hz, Ø0.150 mm)
0.3 J/cm2 (355 nm, 10 ns, 10 Hz, Ø0.381 mm)
300 W/cm (1.064 µm, Ø0.044 mm)
500 W/cm (10.6 µm, Ø0.339 mm)
Protected Aluminum
(-G01)
450 nm - 20 µm >90% (450 nm - 2 µm)
>95% (2 - 20 µm)
info 0.3 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø1.000 mm)  100 W/cm (1.070 µm, Ø0.098 mm)
350 W/cm (10.6 µm, Ø0.339 mm)
Ultrafast-Enhanced Silver
(-AG)
750 nm - 1 µm RS > 99.0%
RP > 98.5%
info 0.18 J/cm2 (800 nm, 52 fs FWHM S-Pol, 1000 Pulses)
0.39 J/cm2 (800 nm, 52 fs FWHM S-Pol, Single Pulse)
-
Protected Silver (-P01) 450 nm - 20 µm >97.5%
(450 nm - 2 µm)
>96% (2 - 20 µm)
info 0.225 J/cm2 (800 nm, 99 fs, 1 kHz, Ø0.167 mm)
3 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø1.000 mm)
500 W/cm (1.07 µm, Ø0.974 mm)
1500 W/cm (10.6 µm, Ø0.339 mm)
Protected Silver (-P02)e 450 nm - 20 µm >97% (450 nm - 2 µm)
>95% (2 - 20 µm)
info - -
Protected Gold (-M01) 800 nm - 20 µm >96% info 2 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø1.000 mm) 500 W/cm (1.070 µm, Ø0.089 mm)
750 W/cm (10.6 µm, Ø0.339 mm)
MIR Enhanced Gold
(-M02)
2 - 20 µm >98% info 0.1 J/cm2 (1.064 µm, 10 ns, 10 Hz, Ø1.06 mm)
3 J/cm2 (10.6 µm, 100 ns, 1 Hz, Ø1.29 mm)
25 W/cm (1.07 µm, Ø1.04 mm)
450 W/cm (10.6 µm, Ø1.18 mm)
Unprotected Gold (-M03) 800 nm - 20 µm >97% info 4 J/cm2 (10.6 µm, 100 ns, 1 Hz, Ø0.435 mm) 1000 W/cm (10.6 µm, Ø1.18 mm)
  • Click each link to view our standard fused silica mirror offerings with that coating. Click here to view our complete line of HR-coated optics.
  • The reflectance is measured over the specified wavelength range and then averaged.
  • All diameters are the 1/e2 values.
  • The power density of your beam should be calculated in terms of W/cm. For an explanation of why the linear power density provides the best metric for long pulse and CW sources, please see the "Continuous Wave and Long-Pulse Lasers" section in the Damage Thresholds tab.
  • This variation of our protected silver coating is only found on the PFR14-P02 Rectangular Mirror.

Narrowband Laser Line HR Coatings
Thorlabs currently offers twelve different laser line HR coatings optimized for various performance parameters. These dielectric HR coatings offer very high reflectance over specific laser line wavelength ranges.


Narrowband Laser Line HR Coating Specifications
Coating Namea Wavelength
Range
Laser Line Average Reflectanceb Angle of 
Incidence
Graphs Pulsed Laser Damage Thresholdc CW Laser Damage Thresholdd
H01 193 nm ArF Excimer >98% (S- and P-Pol) info 3 J/cm2 (10 ns) -
K04 262 - 266 nm Nd:YAG,
4th Harmonic
>99.0% (S- and P-Pol) 0° to 45° info 2 J/cm2 (266 nm, 10 ns, 10 Hz, Ø0.416 mm) -
K05 300 - 308 nm Ar Ion >99.5% (S-Pol)
>98.0% (P-Pol)
0° to 45° info - -
K07 333 - 364 nm Ar Ion >99.5% (S-Pol, 45° AOI)e
>99.0% (P-Pol, 45° AOI)e
>98.7% (Unpol, 0° AOI)e
0° to 45° info 5 J/cm2 (355 nm, 10 ns, 10 Hz, Ø0.294 mm) -
K08 349 - 355 nm Nd:YAG,
3rd Harmonic
>99.5% (S- and P-Pol) 0° to 45° info 3.5 J/cm2 (355 nm, 10 ns, 10 Hz, Ø0.350 mm) -
K10 458 - 528 nm Ar Ion >99.0% (S- and P-Pol) 0° to 45° info - -
J11 520 - 647 nm Kr Ion >99.7% (S- and P-Pol) 45° info - -
K12 524 - 532 nm Nd:YAG,
2nd Harmonic
>99.5% (S-Pol)
>99.0% (P-Pol)
0° to 45° info 8 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.491 mm) 550 W/cm (532 nm, Ø1.000 mm)
K13f
(Dual Coating)
532 nm Nd:YAG,
2nd Harmonic
>98.0% (S- and P-Pol) 0° to 45° info 8 J/cm(532 nm, 10 ns, 10 Hz, Ø0.491 mm) -
1064 nm Nd:YAG >99.0% (S- and P-Pol) 0° to 45° 5 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø1.010 mm)
K14 1047 - 1064 nm Nd:YAG >99.5% (S- and P-Pol) 0° to 45° info 25 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø0.552 mm) 20 kW/cm (1070 nm, Ø0.974 mm)
L01 10.6 µm CO2 >99% (S- and P-Pol) 0° to 45° info 6 J/cm2 (10.6 µm, 100 ns, 1 Hz, Ø0.362 mm) 10 kW/cm (Ø0.115 mm)
  • Click to view our round mirror offerings.
  • Unless otherwise specified, the reflectance is measured over the specified wavelength range and then averaged.
  • All diameters are the 1/e2 values.
  • The power density of your beam should be calculated in terms of W/cm. For an explanation of why the linear power density provides the best metric for long pulse and CW sources, please see the "Continuous Wave and Long-Pulse Lasers" section in the Damage Thresholds tab.
  • For our K07 coating, we specify the minimum reflectance at 352 nm.
  • We also offer unmounted and cage-cube-mounted right angle prism mirrors.

Crystalline Mirror Coatings
Thorlabs Crystalline Solutions currently offers three different GaAs/AlGaAs crystalline coatings optimized for superior mid-IR performance, as well as the ability to create custom crystalline coatings. These high-reflectance mirror coatings are ideal for high-finesse laser cavities, precision interferometry, and high-power laser systems. The specifications below are typical values, and each mirror is made to order by request through Tech Support.

Crystalline HR Coating Specifications
Coating Namea Center Wavelengths
Available Between
Reflectanceb Loss Angle Pulsed Laser Damage Thresholdc CW Laser Damage Thresholdd
xtal stable™ 900 nm and 2.0 µm >99.99% (Typical)
>99.999% (Max)
<4 x 10-5 at 300 K
<5 x 10-6 at 10 K
5 J/cm2 (1030 nm, 10 ns, 10 Hz, Ø0.240 mm) 46.2 kW/cm (1064 nm, Ø5.5 mm)
xtal mir™ 2.0 µm and 5.0 µm
xtal therm™ 900 nm and 5.0 µm
  • Click to view our mirror offerings.
  • Partial transmission can be tuned per customer request. 
  • All diameters are the 1/e2 values.
  • The power density of your beam should be calculated in terms of W/cm. For an explanation of why the linear power density provides the best metric for long pulse and CW sources, please see the "Continuous Wave and Long-Pulse Lasers" section in the Damage Thresholds tab.

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/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.

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).


Posted Comments:
Ricardo Ramirez  (posted 2019-07-23 14:26:19.017)
I'm wondering if you have the capability to produce a metallic coating on a polycarbonate window (.236 inch thick 4 feet in diameter).
YLohia  (posted 2019-07-23 03:51:40.0)
Hello, I have reached out to you directly regarding this. Custom items can be requested by emailing techsupport@thorlabs.com.
gsimpson  (posted 2019-01-30 12:00:03.84)
We need to deliver 1064 and 532 nm light through a 6-element lens set. The very best coating is clearly the V-coating for the YAG harmonics, but it is only available for the planoconvex lenses. We also have two plano-concave , a bi-convex, and a mesiscus lens we need to integrate. 1. Can these be purchased with the V-coating, and if so at what price? 2. Can we track down data on the anticipated losses using the A or C coatings? The available spectral windows online do not include both the lowest YAG harmonics in the curves. Thanks, Garth
YLohia  (posted 2019-01-30 03:21:03.0)
Hello Garth, thank you for contacting Thorlabs. Custom coatings on our optics can be requested by emailing techuspport@thorlabs.com. We will reach out to you with information about this and the extended transmission plots for the A and C coatings.
blanch  (posted 2018-12-14 14:47:07.61)
To whom it may concern, I am working at IFAE, a laboratory on particle physics in Barcelona (Spain), where we develop instrumentation of scientific instruments. We currently need a photo sensitive device that reflects less than 0.5-1% of 1064 nm light. For that the 1064 nm Antireflection Coating may nicely work. The final goal is to allow most of the light pass and then trap to avoid 1064 nm light is reflected back. In this sense the material where the coating is made is relevant. We need a kind of filter, we do not need a lens. Can you provide information on which options are in terms of the material? Concerning dimension, we have not them fixed but they would be at the level of few cm squares. Additionally, the element will need to be in vacuum (10-9) and high temperatures (150 degrees).So, if you have information on that is also important. Thanks, Oscar
llamb  (posted 2018-12-18 10:19:26.0)
Hello Oscar, thank you for your feedback. In terms of vacuum compatibility, we do not test our parts beyond 10^-8 Torr, where our vacuum viewports are certified. While we cannot comment on behavior at 10^-9 Torr, we do not expect any issues at that lower pressure for our dielectric optical coatings. As for 150°C temperatures, we also would not expect any issues with our dielectric coatings, as long as the temperature is kept at a consistent temperature rather than cycled high and low. It sounds like a notch filter could be most useful for you to "trap" 1064 nm wavelengths after passing through the AR coating. I will reach out to you directly to discuss your application further.
j.kurtz  (posted 2018-09-09 17:19:55.253)
I would like to know what materials are used in your broad-band AR coatings. I'm particularly interested in the materials in the AR-B coating for purposes of evaluating their compatibility with the low-earth orbit environment. Cheers, Joe
nbayconich  (posted 2018-09-14 02:47:12.0)
Thank you for contacting Thorlabs. Unfortunately the materials used in our coating designs are proprietary information. I will reach out to you directly to discuss your application.
wandner  (posted 2018-08-13 14:14:04.123)
Sehr geehrte Damen und Herren, ich wäre Ihnen sehr dankbar, wenn Sie mir mitteilen könnten, wie sich A AR-Coating im Bereich 800 bis 1000 nm verhält. Viele Grüße Karl Wandner
swick  (posted 2018-08-28 05:13:34.0)
This is a response from Sebastian at Thorlabs. Thank you for the inquiry. I contacted you directly with the data requested. (Ich habe Sie kontaktiert und die angefragten Daten zugeschickt.)
ismael  (posted 2018-07-23 07:22:03.26)
Hi, I am modeling the SOLIS3C source in Zemax and I wanted to know how to model the scattering properties of the frontal face of said source. Is there a particular black coating to use for this purposes? thanks.
nreusch  (posted 2018-07-27 07:33:55.0)
This is a response from Nicola at Thorlabs. Thank you for your inquiry. For analyzing the scattering properties for our SOLIS LEDs, we recommend to use a tool called LensMechanix that comes with different scattering profiles. However, Zemax OpticStudio also provides different materials as well as a coating file that could be used and edited. SOLIS LEDs contain different materials at the front face of the housing. The choice of the best suited coating therefore depends on the exact part of the housing you would like to model. We will contact you directly to provide further assistance.
vitaly.tsukanov  (posted 2018-07-17 14:10:14.873)
Dear Thorlabs! Can you provide the band-pass filter interference coatings on the surfaces with high positive curvature, for example, sphere or hemisphere? The transmission features of this coating should be even over all sphere/hemisphere.surface. thank you in advance! Vitaly Tsukanov.
YLohia  (posted 2018-07-17 10:13:50.0)
Hello Vitaly, thank you for contacting Thorlabs. One thing to note is that these coatings are designed for specific AOIs since the performance is dependent on that. With a spherical design, the AOIs will be all over the place. We will reach out to you directly via email to discuss this further.
v.t.tenner  (posted 2018-01-16 13:48:16.467)
I am designing a broad-band optical system, with wavelengths between 300 and 1000nm. Do you have specifications of the B coating in the wavelength range between 300 and 650 nm, and for the A coating in the wavelenght range of 650-1000nm?
tfrisch  (posted 2018-01-16 10:13:57.0)
Hello, thank you for contacting Thorlabs. While we don't specify the out-of-band performance of our AR coatings, I'd expect over such a large range that there would be significant reflection peaks. These would change from one coating run to another, but I would not be surprised to see peaks of 10-40% at some out-of-band wavelengths. Uncoated optics may be better for your application. I will reach out to you with more details.
drvanaidu  (posted 2017-12-12 20:32:48.147)
hello sir, Thor labs optical coatings are very nice and useful information. plz tell me how to design and what materials are required for HR COATINGS
nbayconich  (posted 2017-12-13 05:19:15.0)
Thank you for contacting Thorlabs. Unfortunately our coating designs are proprietary information. Dielectric reflective coatings consist of multiple layers of varying high and low refractive indexes. The coatings are created by stacking different dielectric materials on top of one another and the thickness of these layers and number of layers create the reflectivity at a specified design wavelength range.
moonbs21  (posted 2017-05-15 16:47:32.117)
I appreciate your delicate products. Can you provide dielectric coated "glass slide" and "cover slip"? Thank you.
tfrisch  (posted 2017-05-19 03:21:21.0)
Hello, thank you for contacting Thorlabs. We can offer many different coatings for different substrates. I will reach out to you about the needs of your application.
kritter  (posted 2017-01-27 15:07:53.123)
If I cement an optical window with a C coating to another element using Norland NOA 60, what will be the reflection at the coating/cement interface at 1550nm?
tfrisch  (posted 2017-02-16 02:39:38.0)
Hello, thank you for contacting Thorlabs. All of our anti-reflection coatings are designed for a glass-air interface, and using an adhesive like NOA60 on the surface would disrupt that design. It would not continue to function as an anti-reflective coating. I will reach out to you directly to discuss this.
kirill.gapanovich  (posted 2017-01-09 13:20:55.42)
Kind Thorlabs, is it possible to receive from you coating files for LightTools? Or, if it is not possible to provide coating data for LightTools, could you please provide table data for THORA and THORB coatings, and I will make coating files by myself.
tfrisch  (posted 2017-01-09 02:00:37.0)
Hello, thank you for contacting Thorlabs. Unfortunately, the prescriptions of our AR coatings are proprietary, and we are unable to provide the tabular data or a model for them. You can however use the typical reflectance curves we give as a guide. I will reach out to you directly.
ck.chew  (posted 2016-10-17 16:28:29.11)
Could Thorlabs provide AR coating 'C' 1050-1700nm service for Asperic Lens ACL25416U? If yes, 1. how much for ACL25416U-C? 2. MOQ? Rgds, CK Chew
jlow  (posted 2016-10-18 04:31:43.0)
Response from Jeremy at Thorlabs: I will contact you directly about this.
mchen  (posted 2016-07-21 10:38:25.673)
Hi, Can you do D and F AR coating on AgGaSe2 crystal? Thanks, Mike
Lev.F  (posted 2016-06-26 06:41:41.553)
Dear Thorlabs, we are looking optical windows operated at 900+/-20nm wavelength with 60+/-5 degrees AOI. Would you please give us transmission curves for s- and -p polarization components for your BB AR B-coating on N-SF11 glass? This coating is used for your Anamorphic Prisms. Thank you!
peter  (posted 2016-06-22 08:45:49.803)
Dear Thorlabs, what is the reflectance of the lens with C coating for wavelength 850 nm? Thank you!
besembeson  (posted 2016-06-22 12:09:47.0)
Response from Bweh at Thorlabs USA: You could have as much as 18% loss in reflection from each surface from the antireflection coating. Please contact me at techsupport@thorlabs.com for a typical reflectivity data of the AR coating outside its design range.
cf1546  (posted 2015-01-30 09:12:35.8)
Dear Thorlabs team, in the HR coating tab you state the materials of the overcoat of protected silver (SiO2) and UV-enhanced aluminum (MgF2), but not of the protected gold. Due to material compatibility considerations, it would be nice if you could tell me i) if the overcoat of protected gold mirrors is the same / comparable to the one of protected silver in material and deposition method (EBD?), and ii) if there are any fluorine-containing chemical compounds like MgF2 present in protected silver or gold mirrors. Thank you!
myanakas  (posted 2015-03-30 10:43:08.0)
Response from Mike at Thorlabs: Thank you for your feedback. We are currently unable to specify the exact composition of the overcoat on our gold coated surface.
hha07  (posted 2014-09-24 14:29:09.29)
The raw data xlsx file supplies reflectivities for the various HR coatings. What polarization and angle was used for this data or is it an average? Specifically I am worried about the reflectivity at 8 degree and 45 degree for wavelengths at the edge of the range for E02 at e.g. 397 and 866 nm.
besembeson  (posted 2014-10-23 02:12:49.0)
Response from Bweh: These plots and data, with the polarization states and incidence angles specified for 355nm to 920nm can be found at the following link: http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=139&tabname=Reflectance%20Plots
magnus.schloesser  (posted 2014-05-07 12:52:19.963)
In our optical setup we observed laser induced contamination on half-wave plates (WPMQ05M-532). The power density on the optic was about 30 W/cm². All other components (N-BK7 lenses, Glan-Taylor polarizer, Mirrors, ...) do not show these contaminations. We assume that this may be related to different "chemical reactions" on the different coating surfaces of the optics. Could you tell us the production methods (EBD, IAD, ...) of the WPMQ05M-532, a BBAR - A and a HR E02 coating? What is the material is forming the most outer layer (being the one in contact with the ambient air.)? Thanks in advance!
jlow  (posted 2014-06-12 02:08:48.0)
Response from Jeremy at Thorlabs: We have not seen this issue before and we use similar coatings on other optic parts. It would be good to see if cleaning the surfaces of the wave-plates would remove this issue you are having. I will contact you directly to get more detail on this.
J.Boterman  (posted 2013-11-27 10:40:28.703)
Is data available on the AR-B coating for wavelengths outside the nominal range?
tcohen  (posted 2013-12-05 02:52:43.0)
Response from Tim at Thorlabs: Thanks for your inquiry. There will be variations in coating runs but we can supply representative out of band data. I've emailed you to discuss your wavelengths.
andrea.farina  (posted 2013-09-11 13:35:17.94)
Kind Thorlabs, is it possible to have the COATING file for ZEMAX for simulation fo your lenses? If I open a lens file ZMX provided by you the program tell me that is no present the file COATINGTHOR. Can I have it? thank you again Andrea Farina
jlow  (posted 2013-09-11 09:05:00.0)
Response from Jeremy at Thorlabs: We now supply both the ZAR file and the ZMX file. The ZAR file provides you with the ZMX file as well as any supporting files. This includes the coating file. You will not run into that issue with the use of the ZAR file.
jlow  (posted 2012-09-28 09:16:00.0)
Response from Jeremy at Thorlabs: Our dichroic coating are designed to be used in air/vacuum. Therefore, putting the coating in direct contact would produce a significant difference in performance.
franxm  (posted 2012-09-20 16:27:40.0)
In general, do you expect a significant difference in dichroic coating performance if the coated side of the substrate is placed in contact with a material with a refractive index ~2?
bdada  (posted 2012-04-23 17:00:00.0)
Response from Buki at Thorlabs: Thank you so much for your feedback. We are expanding our manufacturing capabilities and hope to be able to communicate a coating schedule in the future. Till then, you can request custom coated optics by emailing TechSupport@thorlabs.com.
pkeesser  (posted 2012-04-20 15:18:06.0)
There is really great, can we see a coating schedule thta would show available slots?
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