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Unmounted Absorptive Neutral Density Filters


  • Optical Densities from 0.1 to 8.0
  • Attenuate Visible Light
  • Ø1/2", Ø25 mm, Ø2", and 2" x 2" Sizes Available

NE260B

(2" x 2")

NE2R30B

(Ø2")

NE03B

(Ø25 mm)

NE505B

(Ø1/2")

NE201B in an FH2
Fixed Filter Mount
(See Link to Right)

Related Items


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Selection Guide for Neutral Density Filters
Absorptive
Uncoated (400 - 650 nm) Mounted
Unmounted
Uncoated (800 - 2600 nm) Mounted
Unmounted
AR-Coated (350 - 700 nm) Mounted
Unmounted
AR-Coated (650 - 1050 nm) Mounted
Unmounted
AR-Coated (1050 - 1650 nm) Mounted
Unmounted
Reflective
N-BK7 (350 - 1100 nm) Mounted
Unmounted
UV Fused Silica (200 - 1200 nm) Mounted
Unmounted
ZnSe (2 - 16 µm) Mounted
Unmounted
Wedged Reflective
Variable Reflective
Neutral Density Filter Kits
Optic Cleaning Tutorial

Features

  • Four Sizes Available:
    • Ø1/2"
    • Ø25 mm
    • Ø2"
    • 2" x 2"
  • Optical Densities Ranging from 0.1 to 8.0
  • Ideal for Low-Power Applications (<1 W, see the Specs Tab for Additional Details)
  • Absorptive Glass Reduces Multiple Reflections
  • Edge Blackening Available Upon Request

Our absorptive neutral density (ND) filters are available with optical densities (OD) ranging from 0.1 to 8.0. They are offered in sizes of Ø1/2", Ø25 mm, Ø2", or 2" x 2". Unlike their reflective, metallic counterparts, each filter is fabricated from a Schott glass substrate that has been selected for its spectrally flat absorption coefficient in the visible region of 400 - 650 nm. By varying the type and thickness of the glass used, we are able to produce the entire line of absorptive ND filters from just four types of Schott glass. Because of variations between different lots of glass, Thorlabs recommends that the user calibrate the filter in their setup before taking quantitative measurements. The Specs tab contains the typical transmission and damage threshold of each filter type, while the Graphs tab contains transmission and reflectivity curves for the 300 - 1100 nm wavelength range.

The round filters listed on this page are also available in threaded mounts that are engraved with the optical density and part number. The 2" x 2" filters are only available unmounted, but are compatible with Thorlabs' family of fixed filter mounts. Filter kits containing a selection of the filters shown here are also available, as is a lockable metal case with a foam insert for storing loose square filters. For more information, please see below.

Please note that these products are not designed for use as laser safety equipment. For lab safety, Thorlabs offers an extensive line of safety and blackout products, including beam blocks, that significantly reduce exposure to stray light.

Filter Sizes Ø1/2" Ø25 mm Ø2" 2" x 2"
Diameter Tolerance +0.0 / -0.25 mm
Clear Aperture 90% Outer Diameter 90% of Total Area
Surface Flatness
(@ 633 nm)
λ/4 λ
Surface Quality 40-20 Scratch-Dig
Parallelism <3 arcmin <10 arcsec
Substrates NG1, NG4, NG9, or NG11 (Schott Glass)
Damage Thresholds
OD 0.2 Filters Pulsed 10 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.456 mm)
OD 1.0 Filters CWa,b 50 W/cm (532 nm, Ø0.019 mm)
Pulsed 10 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.504 mm)
OD 4.0 Filters Pulsed 5 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.340 mm)
OD 6.0 Filters Pulsed 5 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.340 mm)
  • 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 Damage Thresholds tab.
  • CW testing for these filters was performed using a 30 second exposure at each test site.
Optical Density
(@ 633 nm)
Theoretical Transmissiona
(@ 633 nm)
Substrate Thicknessb Substrate
0.1 ± 0.01 77.6 to 81.3% 0.56 mm NG11
0.2 ± 0.01 61.7 to 64.6% 1.43 mm NG11
0.3 ± 0.01 50% 2.30 mm NG11
0.4 ± 0.02 40% 0.71 mm NG4
0.5 ± 0.03 32% 0.91 mm NG4
0.6 ± 0.04 25% 1.10 mm NG4
1.0 ± 0.06 10% 1.89 mm NG4
1.3 ± 0.08 5% 2.48 mm NG4
2.0 ± 0.10 1% 1.40 mm NG9
3.0 ± 0.15 0.1% 2.11 mm NG9
4.0 ± 0.20 1.0x10-2% 2.83 mm NG9
5.0 ± 0.25 1.0x10-3% 3.55 mm NG9
6.0 ± 0.30 1.0x10-4% 1.5 mm NG1
7.0 ± 0.35 1.0x10-5% 1.7 mm NG1
8.0 ± 0.40 1.0x10-6% 1.9 mm NG1

a If desired, Thorlabs can measure the transmission of most of these filters prior to shipment. Please contact Technical Support for a quote.
b The actual thickness of each ND filter depends upon the optical density of the lot of glass used to manufacture the filter.

Optical Density

The optical density, OD, is defined by the equation:

Optical Density Equation

Hence, a higher OD corresponds to lower transmission and greater reflection of the incident light, while a lower OD corresponds to higher transmission and less reflection. For example, an OD = 2 filter will attenuate the transmitted beam to 1% of the incident intensity.

For Detailed Plot Information
For More InfoPlease use the icon shown to the left in the product listings for plots of the wavelength-dependent transmission (and optical density) for each filter type. Excel files containing the raw data used to make these plots are also available for download.
 Transmission
Raw Data files are available for each part by clicking on the blue "info icons" below.
Reflectivity
An Excel file with 8° AOI reflectivity data is also available.
OD 0.1 - 0.6
OD 1.0 - 2.0
OD 3.0 - 4.0

Click for Transmission in the 400 - 700 nm Wavelength Range

OD 5.0 - 6.0
OD 7.0 - 8.0

Line On GraphWavelength RangeTypeMaterialCoatingMounting
NDIRxx2000 - 16,000 nm ReflectiveZnSeInconel Unmounted and Mounted
NENIRxx-C1050 - 1620 nmAbsorptiveSchott GlassC-CoatedUnmounted and Mounted
NENIRxx800 - 2600 nmAbsorptiveSchott GlassUncoatedUnmounted
Mounted
NExx-B650 - 1050 nmAbsorptiveSchott GlassB-CoatedUnmounted
Mounted
NExx400 - 650 nmAbsorptiveSchott GlassUncoatedUnmounted
Mounted
NDxx350 - 1100 nmReflectiveN-BK7Inconel Unmounted
Mounted
NExx-A350 - 700 nmAbsorptiveSchott GlassA-CoatedUnmounted
Mounted
NDUVxx200 - 1200 nmReflectiveUVFSInconel Unmounted
Mounted

 

Damage Threshold Specifications
Optical Density Damage Threshold
0.2 Pulsed 10 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.456 mm)
1.0 CWa,b 50 W/cm (532 nm, Ø0.019 mm)
Pulsed 10 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.504 mm)
4.0 Pulsed 5 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.340 mm)
6.0 Pulsed 5 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.340 mm)
  • 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 below.
  • CW testing for these filters was performed using a 30 second exposure at each test site.

Damage Threshold Data for Thorlabs' Absorptive ND Filters

The specifications to the right are measured data for Thorlabs' absorptive neutral density filters. Damage threshold specifications are constant for a given optical density, regardless of the size of the filter.

 

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.


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Posted Comments:
Poster:martin.gersing
Posted Date:2017-01-17 15:06:41.697
Dear Thorlabs, is there a maximum average input power for your absorptive ND-Filters? I can only find damage thresholds maximum power density. Thanks in advance.
Poster:tfrisch
Posted Date:2017-01-19 03:01:35.0
Hello, thank you for contacting Thorlabs. I will reach out to you for more details on your source.
Poster:mg9420
Posted Date:2016-07-25 04:51:42.26
What is the transmission of the filter NE501B at high pulse energy? Is transmission change at high pulse energy?
Poster:kaccie
Posted Date:2015-05-22 11:01:40.153
What's the typical tolerance on the thickness of these filters? I've seen tolerances as high as 0.5 mm on 2.5-mm nominally thick filters from another vendor!
Poster:jlow
Posted Date:2015-05-22 03:11:17.0
Response from Jeremy at Thorlabs: These are absorptive ND filters and the thickness is directly related to the optical density. The main specification we control is the optical density (see the specs tab for more detail on the tolerance) and the thickness is whatever it is to get to the specified optical density. If you require a specific well-controlled thickness, we have the reflective ND filter that you can possibly use.
Poster:k.regenfelder
Posted Date:2014-04-14 09:41:43.03
Dear all, would it be possible to get this product in 3"x3" dimension or min. 7,5x7,5cm? Kind regards, Katja Regenfelder
Poster:jlow
Posted Date:2014-04-15 08:30:18.0
Response from Jeremy at Thorlabs: Yes we can offer larger size version of these absorptive ND filters. We will contact you directly for the quote.
Poster:fabian.stutzki
Posted Date:2013-10-10 13:41:44.803
Hi, could you please include measurements for a larger wavelength scale - I expect, that these neutral density absorptive filters can be used at 1.5, 2 or even larger wavelengths. Is this correct? Best regards Fabian Stutzki
Poster:jlow
Posted Date:2013-10-23 13:14:00.0
Response from Jeremy at Thorlabs: We are working on taking the scans for longer wavelengths. These do have transmission out past 2µm but the optical density will be much lower than specified. We will get in contact with you to discuss about this further.
Poster:brooksc33
Posted Date:2013-09-25 04:25:02.93
This message is just to bring to your attention that the data given in the Excel file for the filter NE01B appears to be wrong. I downloaded the data from the link that appears in the window of the graph that pops up when one clicks the information icon (blue diamond with white 'i' inside). From the extra tab on the sheet I downloaded it looks like the data given is for item BSW16. I used the data from filter NE501B assuming that these two filters are made from the same material.
Poster:sharrell
Posted Date:2013-09-25 09:21:00.0
Response from Sean at Thorlabs: Thank you for bringing the error in the Excel file to our attention. We’ve updated the file. You are correct that the only difference between the NE01B and the NE501B is the outer diameter.
Poster:bdada
Posted Date:2011-10-26 00:32:00.0
Response from Buki at Thorlabs: Thank you for your feedback. On our website we provide the following damage threshold guideline for our absorptive ND filter when using pulsed light: 8 J/cm2 (1064 nm, 10 ns, 10 Hz, Ø1.040 mm) 20 J/cm2 (1542 nm, 10 ns, 10 Hz, Ø0.144 mm) For CW light, the guideline is 100W/cm^2 with a 1mm beam diameter at 532nm. We also have beam traps that can handle up to 150W/cm^2 or 40J/cm^2. Below is a link with more information. We will contact you to discuss your application further to ensure you select the right optical components. Please contact TechSupport@thorlabs.com if you have questions. http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=1449
Poster:bdada
Posted Date:2011-10-25 23:59:00.0
Response from Buki at Thorlabs: Thank you for using our Web Feedback. As a guideline, please use 25W/cm^2 for a 1mm diameter beam at 532nm for the reflective ND filters. For the absorptive ND filters, please use 100W/cm^2 for a 1mm diameter at 532nm. Please contact TechSupport@thorlabs.com if you have further questions.
Poster:nomis.fischer
Posted Date:2011-10-20 13:10:27.0
Dear Thorlabs Team, can a ND 3 or ND 6 absorptive filter be used to fully absorb the energy of a pulsed laser, which has the following characteristics: puls duration under 10 femtoseconds, bandwidth 820nm, pulse repetition rate 70-120Mhz, beam diameter 2mm, peak power (@75 Mhz) 1000kW. My purpose is to use the filter as a kind of beam trap. Thank you in andvance. Simon Fischer
Poster:ludek.lovicar
Posted Date:2011-10-19 16:48:08.0
Dear Mrs/Mr, can be used the ND filters (absorptive or reflective) for 150mW CW laser (473nm) without damaging of the filters? The filter would be placed approx. 20 mm away from a laser output and should transmit only approx. 1% of output laser power. If not, what would you recommend me for attenuation of laser power? Thank you for prompt reply. Kind regards, Ludek Lovicar

Unmounted Ø1/2" Absorptive Neutral Density Filters

Item #Optical Density*
(Transmission)
Transmission Data
NE501B 0.1 (79%) More Info Icon
NE502B 0.2 (63%) More Info Icon
NE503B 0.3 (50%) More Info Icon
NE504B 0.4 (40%) More Info Icon
NE505B 0.5 (32%) More Info Icon
NE506B 0.6 (25%) More Info Icon
NE510B 1.0 (10%) More Info Icon

*At 633 nm

Item #Optical Density*
(Transmission)
Transmission Data
NE513B 1.3 (5%) More Info Icon
NE520B 2.0 (1%) More Info Icon
NE530B 3.0 (0.1%) More Info Icon
NE540B 4.0 (0.01%) More Info Icon
NE550B 5.0 (1x10-3%) More Info Icon
NE560B 6.0 (1x10-4%) More Info Icon

Click on More Info Icon for a plot and downloadable data. The black dashed line indicates the designated optical density.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
NE501B Support Documentation
NE501BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 0.1
$19.90
Today
NE502B Support Documentation
NE502BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 0.2
$19.90
Today
NE503B Support Documentation
NE503BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 0.3
$19.90
Today
NE504B Support Documentation
NE504BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 0.4
$19.90
Today
NE505B Support Documentation
NE505BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 0.5
$19.90
Today
NE506B Support Documentation
NE506BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 0.6
$19.90
Today
NE510B Support Documentation
NE510BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 1.0
$19.90
Today
NE513B Support Documentation
NE513BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 1.3
$19.90
Today
NE520B Support Documentation
NE520BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 2.0
$19.90
Today
NE530B Support Documentation
NE530BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 3.0
$19.90
Today
NE540B Support Documentation
NE540BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 4.0
$19.90
Today
NE550B Support Documentation
NE550BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 5.0
$19.90
Today
NE560B Support Documentation
NE560BUnmounted Ø1/2" Absorptive ND Filter, Optical Density: 6.0
$19.90
Today

Unmounted Ø25 mm Absorptive Neutral Density Filters

Item #Optical Density*
(Transmission)
Transmission Data
NE01B 0.1 (79%) More Info Icon
NE02B 0.2 (63%) More Info Icon
NE03B 0.3 (50%) More Info Icon
NE04B 0.4 (40%) More Info Icon
NE05B 0.5 (32%) More Info Icon
NE06B 0.6 (25%) More Info Icon
NE10B 1.0 (10%) More Info Icon
NE13B 1.3 (5%) More Info Icon

*At 633 nm

Item #Optical Density*
(Transmission)
Transmission Data
NE20B 2.0 (1%) More Info Icon
NE30B 3.0 (0.1%) More Info Icon
NE40B 4.0 (0.01%) More Info Icon
NE50B 5.0 (1x10-3%) More Info Icon
NE60B 6.0 (1x10-4%) More Info Icon
NE70B 7.0 (1x10-5%) More Info Icon
NE80B 8.0 (1x10-6%) More Info Icon

Click on More Info Icon for a plot and downloadable data. The black dashed line indicates the designated optical density.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
NE01B Support Documentation
NE01BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.1
$32.75
Today
NE02B Support Documentation
NE02BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.2
$32.75
Today
NE03B Support Documentation
NE03BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.3
$32.75
Today
NE04B Support Documentation
NE04BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.4
$32.75
Today
NE05B Support Documentation
NE05BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.5
$32.75
Today
NE06B Support Documentation
NE06BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.6
$32.75
Today
NE10B Support Documentation
NE10BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 1.0
$32.75
Today
NE13B Support Documentation
NE13BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 1.3
$32.75
Today
NE20B Support Documentation
NE20BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 2.0
$32.75
Today
NE30B Support Documentation
NE30BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 3.0
$32.75
Today
NE40B Support Documentation
NE40BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 4.0
$32.75
Today
NE50B Support Documentation
NE50BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 5.0
$32.75
Today
NE60B Support Documentation
NE60BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 6.0
$32.75
Today
NE70B Support Documentation
NE70BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 7.0
$32.75
Today
NE80B Support Documentation
NE80BUnmounted Ø25 mm Absorptive ND Filter, Optical Density: 8.0
$32.75
Today

Unmounted Ø2" Absorptive Neutral Density Filters

Item #Optical Density*
(Transmission)
Transmission Data
NE2R01B 0.1 (79%) More Info Icon
NE2R02B 0.2 (63%) More Info Icon
NE2R03B 0.3 (50%) More Info Icon
NE2R04B 0.4 (40%) More Info Icon
NE2R05B 0.5 (32%) More Info Icon
NE2R06B 0.6 (25%) More Info Icon
NE2R10B 1.0 (10%) More Info Icon
*At 633 nm
Item #Optical Density*
(Transmission)
Transmission Data
NE2R13B 1.3 (5%) More Info Icon
NE2R20B 2.0 (1%) More Info Icon
NE2R30B 3.0 (0.1%) More Info Icon
NE2R40B 4.0 (0.01%) More Info Icon
NE2R50B 5.0 (1x10-3%) More Info Icon
NE2R60B 6.0 (1x10-4%) More Info Icon
Click on More Info Icon for a plot and downloadable data. The black dashed line indicates the designated optical density.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
NE2R01B Support Documentation
NE2R01BUnmounted Ø2" Absorptive ND Filter, Optical Density: 0.1
$76.50
Today
NE2R02B Support Documentation
NE2R02BUnmounted Ø2" Absorptive ND Filter, Optical Density: 0.2
$76.50
Today
NE2R03B Support Documentation
NE2R03BUnmounted Ø2" Absorptive ND Filter, Optical Density: 0.3
$76.50
Today
NE2R04B Support Documentation
NE2R04BUnmounted Ø2" Absorptive ND Filter, Optical Density: 0.4
$76.50
Today
NE2R05B Support Documentation
NE2R05BUnmounted Ø2" Absorptive ND Filter, Optical Density: 0.5
$76.50
Today
NE2R06B Support Documentation
NE2R06BUnmounted Ø2" Absorptive ND Filter, Optical Density: 0.6
$76.50
Today
NE2R10B Support Documentation
NE2R10BUnmounted Ø2" Absorptive ND Filter, Optical Density: 1.0
$76.50
Today
NE2R13B Support Documentation
NE2R13BUnmounted Ø2" Absorptive ND Filter, Optical Density: 1.3
$76.50
Today
NE2R20B Support Documentation
NE2R20BUnmounted Ø2" Absorptive ND Filter, Optical Density: 2.0
$76.50
Today
NE2R30B Support Documentation
NE2R30BUnmounted Ø2" Absorptive ND Filter, Optical Density: 3.0
$76.50
Today
NE2R40B Support Documentation
NE2R40BUnmounted Ø2" Absorptive ND Filter, Optical Density: 4.0
$76.50
Today
NE2R50B Support Documentation
NE2R50BUnmounted Ø2" Absorptive ND Filter, Optical Density: 5.0
$76.50
Today
NE2R60B Support Documentation
NE2R60BUnmounted Ø2" Absorptive ND Filter, Optical Density: 6.0
$76.50
Today

Unmounted 2" x 2" Absorptive Neutral Density Filters

Item #Optical Density*
(Transmission)
Transmission Data
NE201B 0.1 (79%) More Info Icon
NE202B 0.2 (63%) More Info Icon
NE203B 0.3 (50%) More Info Icon
NE204B 0.4 (40%) More Info Icon
NE205B 0.5 (32%) More Info Icon
NE206B 0.6 (25%) More Info Icon
NE210B 1.0 (10%) More Info Icon

*At 633 nm

Item #Optical Density*
(Transmission)
Transmission Data
NE213B 1.3 (5%) More Info Icon
NE220B 2.0 (1%) More Info Icon
NE230B 3.0 (0.1%) More Info Icon
NE240B 4.0 (0.01%) More Info Icon
NE250B 5.0 (1x10-3%) More Info Icon
NE260B 6.0 (1x10-4%) More Info Icon

Click on More Info Icon for a plot and downloadable data. The black dashed line indicates the designated optical density.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
NE201B Support Documentation
NE201BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 0.1
$76.50
Today
NE202B Support Documentation
NE202BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 0.2
$76.50
Today
NE203B Support Documentation
NE203BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 0.3
$76.50
Today
NE204B Support Documentation
NE204BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 0.4
$76.50
Today
NE205B Support Documentation
NE205BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 0.5
$76.50
Today
NE206B Support Documentation
NE206BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 0.6
$76.50
Today
NE210B Support Documentation
NE210BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 1.0
$76.50
Today
NE213B Support Documentation
NE213BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 1.3
$76.50
Today
NE220B Support Documentation
NE220BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 2.0
$76.50
Today
NE230B Support Documentation
NE230BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 3.0
$76.50
Today
NE240B Support Documentation
NE240BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 4.0
$76.50
Today
NE250B Support Documentation
NE250BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 5.0
$76.50
Today
NE260B Support Documentation
NE260BUnmounted 2" x 2" Absorptive ND Filter, Optical Density: 6.0
$76.50
Today

Absorptive ND Filter Kits

  • Comprehensive Set of Absorptive ND Filters
  • Ø1/2" (Ø12.7 mm), Ø25 mm (Ø0.98"), Ø2" (Ø50.8 mm), and 2" x 2" (50.8 x 50.8 mm) Versions
  • Round Filters Provided in SM-Threaded Mounts Engraved with OD and Part Number
  • Filters Also Available with OD 6, 7, and 8 (Sold Separately; See Links Below)
  • Additional NBK-7 Mounted Absorptive and Unmounted Absorptive Filters Available
Item # Optic
Size
Mount Included Storage Box Included Optical Densities
NEK02 Ø1/2" SM05 KT02 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1.0, 1.3, 2.0, 3.0, 4.0, 5.0
NEK01 Ø25 mm SM1 KT01 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1.0, 2.0, 3.0, 4.0
NEK03 Ø2" SM2 KT06 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1.0, 2.0, 3.0, 4.0
NEK01S 2" x 2" - KT03 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1.0, 2.0, 3.0, 4.0
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
NEK02 Support Documentation
NEK02Box with 12 Absorptive Ø1/2" ND Filters, SM05-Mounted
$452.00
Today
NEK01 Support Documentation
NEK01Box with 10 Absorptive Ø25 mm ND Filters, SM1-Mounted
$522.00
Today
NEK03 Support Documentation
NEK03Box with 10 Absorptive Ø2" ND Filters, SM2-Mounted
$999.00
Today
NEK01S Support Documentation
NEK01SND Filter Set, 2 x 2 Square Filters, 10 pieces
$779.00
Today

Storage Box for Square Filters

If you purchase individual filters and would like to have a safe, convenient place to store them when not in use, consider our KT03 Storage Box. It holds up to ten 2" x 2" square filters.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
KT03 Support Documentation
KT03Storage Box for Unmounted 2" Square Optics (Max. Capacity: 10)
$83.25
Today
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