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Absorptive and Reflective Neutral Density Filter Kits


  • Reflective and Absorptive ND Kits
  • Laser-Engraved Labels on Mounted Versions
  • Choose from Ø1/2", Ø25 mm, Ø2", and 2"x 2" Sizes

NEK01S

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 - 1700 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

  • Ø1" Mounted Reflective (Metallic) ND Filters Available
  • Ø1/2", Ø25 mm, Ø2", or 2" x 2" Absorptive ND Filters Available
  • 10 Filters Included with Optical Densities from 0.1 - 4.0 (12 Filters from 0.1 - 5.0 for the NEK02)
  • Mounted Versions are Housed in Labeled SM Threaded Lens Tubes
  • Labeled Inserts Hold Filters Securely in Storage Box

Thorlabs' Reflective and Absorptive Neutral Density (ND) Filter Kits offer our most popular filters prepackaged in convenient metal storage boxes. Refer to the Specs (Reflective) and Specs (Absorptive) tabs above for detailed information about the filters included with each kit.

The Ø1/2" Absorptive ND Filters are mounted in SM05 series lens tubes, the Ø25 mm Metallic and Absorptive ND Filters are mounted in SM1 series lens tubes, and the Ø2" absorptive ND filters are mounted in SM2 series lens tubes. In all cases the housing is engraved with the optical density. Same-size lens tubes are stackable, making it possible to create an additive optical density effect. The Absorptive 2" Square Filters can be mounted in our stackable filter holders, also making it possible to create an additive optical density effect.

Each set of filters is housed in a metal box for convenient storage and transportation. Additional storage boxes designed to house mounted Ø25 mm filters (KT01), mounted Ø2" filters (KT06), or unmounted 2" square filters (KT03) can be purchased separately.

 

Optical Density

Optical density (OD) indicates the attenuation factor provided by an optical filter, i.e. how much it reduces the optical power of an incident beam. OD is related to the transmission, T, by the equation
Optical Density Equation
where T is a value between 0 and 1. Choosing an ND filter with a higher optical density will translate to lower transmission. For absorptive filters, this is a result of greater absorption of the incident light, while for reflective filters this is due to greater reflection. A lower optical density filter would be appropriate to achieve higher transmission. As an example, if a filter with an OD of 2 results in a transmission value of 0.01, this means the filter attenuates the beam to 1% of the incident power. Please note that the transmission data for our neutral density filters is provided in percent (%).

Reflective ND Filters

NDK01 Kit - Common Specifications
Substrate N-BK7a
Front Surface Coating Inconel
Spectral Range 350 - 1100 nm
Unmounted Optic Diameter Ø25.0 +0.00/-0.50 mm
Unmounted Optic Thickness 1.0 ± 0.25 mm (unmounted)
Clear Aperture 90% of Optic Diameter
Surface Quality 40-20 Scratch-Dig
Surface Flatness <5λ
Parallelism <3 arcmin
Damage Threshold See Damage Thresholds Tab
  • Click Link for Detailed Specifications on the Substrate
NDK01 Kit Contents
Item # Optical
Density
Nominal
Transmission
Transmission
Data
ND01A 0.1 79% info
ND02A 0.2 63% info
ND03A 0.3 50% info
ND04A 0.4 40% info
ND05A 0.5 32% info
ND06A 0.6 25% info
ND10A 1.0 10% info
ND20A 2.0 1.0% info
ND30A 3.0 0.10% info
ND40A 4.0 0.01% info

UV Reflective ND Filters

NUK01 Kit - Common Specifications
Substrate UV Fused Silicaa
Front Surface Coating Inconel
Spectral Range 200 - 1200 nm
Unmounted Optic Diameter Ø25.0 +0.00/-0.50 mm
Unmounted Optic Thickness 1.0 ± 0.25 mm (unmounted)
Clear Aperture 90% of Optic Diameter
Surface Quality 40-20 Scratch-Dig
Surface Flatness <5λ
Parallelism <3 arcmin
Damage Threshold (CW) See Damage Thresholds Tab
  • Click Link for Detailed Specifications on the Substrate
NUK01 Kit Contents
Item # Optical
Density
Nominal
Transmission
Transmission
Data
NDUV01A 0.1 79% info
NDUV02A 0.2 63% info
NDUV03A 0.3 50% info
NDUV04A 0.4 40% info
NDUV05A 0.5 32% info
NDUV06A 0.6 25% info
NDUV10A 1.0 10% info
NDUV20A 2.0 1.0% info
NDUV30A 3.0 0.10% info
NDUV40A 4.0 0.01% info

Absorptive ND Filter Specifications

Item # NEK02 NEK01 NEK03 NEK01S
Filter Size Ø1/2" Ø25 mm Ø2" 2" X 2"
Number of Filters in Kit 12 10 10 10
Diameter Tolerance +0.0 / -0.25 mm
Clear Aperture 90% of Outer Diameter 90% of Total Area
Surface Flatness @ 633 nm λ/4 λ
Surface Quality 40-20 Scratch-Dig
Parallelism <3 arcmin <10 arcsec
Substrate Material NG4, NG9, or NG11 (Schott)
Damage Threshold See Damage Thresholds Tab
Filter Mount Engraved
SM05L03
Engraved
SM1L03
Engraved
SM2L03
Unmounted

 

Kit Contents

NEK02 NEK01 NEK03 NEK01S Optical
Density
(@ 633 nm)
Theoretical
Transmission
(@ 633 nm)
Transmission
Dataa
Substrate
Thicknessb
Substrate
Ø1/2" Ø1" Ø2" 2" x 2"
NE501A NE01A NE2R01A NE201B 0.1 ± 0.01 77.6 to 81.3% info 0.56 mm NG11
NE502A NE02A NE2R02A NE202B 0.2 ± 0.01 61.7 to 64.6% info 1.43 mm NG11
NE503A NE03A NE2R03A NE203B 0.3 ± 0.01 50% info 2.30 mm NG11
NE504A NE04A NE2R04A NE204B 0.4 ± 0.02 40% info 0.71 mm NG4
NE505A NE05A NE2R05A NE205B 0.5 ± 0.03 32% info 0.91 mm NG4
NE506A NE06A NE2R06A NE206B 0.6 ± 0.04 25% info 1.10 mm NG4
NE510A NE10A NE2R10A NE210B 1.0 ± 0.06 10% info 1.89 mm NG4
NE513A -c -c -c 1.3 ± 0.08 5% info 2.48 mm NG4
NE520A NE20A NE2R20A NE220B 2.0 ± 0.10 1% info 1.40 mm NG9
NE530A NE30A NE2R30A NE230B 3.0 ± 0.15 0.1% info 2.11 mm NG9
NE540A NE40A NE2R40A NE240B 4.0 ± 0.20 0.01% info 2.83 mm NG9
NE550A -c -c -c 5.0 ± 0.25 1.0x10-3% info 3.55 mm NG9
  • Transmission data shown applies to neutral density filters of same OD regardless of size or form factor.
  • The actual thickness of each ND filter is dependent on the optical density of the lot of glass used to manufacture each lot of ND filters.
  • These filters are sold separately. Please refer to our individual uncoated ND filters in mounted round and unmounted round or square form factors.

 Optical Density Transmission Reflectivity
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
Damage Threshold Specifications
Optical
Density
Damage Thresholds
0.2 Pulsed 10 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.456 mm)
1.0 Pulsed 10 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.504 mm)
2.0 CWa,b 12 W/cm (532 nm, Ø1.0 mm)
4.0 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 60 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.

 

Damage Threshold Specifications
Optical
Density
Damage Thresholds
0.3 CWa 16 W/cm (532 nm, CW, Ø0.051 mm)
Pulsed 0.025 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.493 mm)
1.0 CWa 5 W/cm (532 nm, CW, Ø0.019 mm)
Pulsed 0.025 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.566 mm)
2.0 CWa 25 W/cm (532 nm, CW, Ø0.049 mm)
Pulsed 0.025 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.493 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.

Damage Threshold Data for Thorlabs' Reflective ND Filters

The specifications to the right are measured data for Thorlabs' reflective neutral density filters. Damage threshold specifications are constant for a given optical density coating, 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/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).

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.


Posted Comments:
pietern  (posted 2017-05-17 16:27:18.26)
Hi I had a look at the damage thresholds for you absorptive and reflective Neutral Density Filters. According to what you list the Absorptive typically have a higher damage threshold than the reflective. Is this true as I have always believed the opposite? Could you please confirm whether the data stated is correct. Regards, Pieter Neethling
tfrisch  (posted 2017-05-19 04:19:35.0)
Hello, thank you for contacting Thorlabs. Though it is not intuitive, yes, these absorptive filters have a higher damage threshold than these reflective filters. The reflective coating is the limiting factor, partly because it is a metallic coating with some non-negligible absorptive component and a smaller volume to disperse the heat. I will reach out to you directly to discuss this.
pickenha  (posted 2014-01-20 09:21:57.677)
Sehr geehrte Damen und Herren, ich benötige ein Angebot für einen Satz Refl. ND Filter NDK01 mit Box. Viele Grüße PD Dr. Rainer Pickenhain Universität Leipzig Institut für Experimentelle Physik II Halbleiterphysik Linnéstraße 5 04103 Leipzig Germany e-mail: pickenha@server1.rz.uni-leipzig.de
jlow  (posted 2014-01-20 08:55:08.0)
Response from Jeremy at Thorlabs: We will contact you on a quote for the NDK01.
klee  (posted 2009-07-29 18:10:45.0)
Response from Ken at Thorlabs to daniel.kraus: Unfortunately, the reflective ND filters are not recommended for pulsed laser use.
daniel.kraus  (posted 2009-07-29 14:23:02.0)
Dear Sir/Madam, are the reflective ND Filters suitable for pulsed laser applications? Kind Regards, Daniel Kraus
klee  (posted 2009-07-29 12:06:37.0)
Response from Ken at Thorlabs to daniel.kraus: Unfortunately, the reflective ND filters are not recommended for pulsed laser use.
Laurie  (posted 2009-02-05 15:09:24.0)
Response from Laurie at Thorlabs to r.a.loch: Thank you for your inquiry and interest in our products. The damage threshold for these absorptive ND filters is ~30W/cm^2 for a CW source. We do not recommend using these filters with pulsed light sources. If you have additional questions, please let us know.
r.a.loch  (posted 2009-02-05 11:37:53.0)
Dear Sir/Madam, What is the damage threshold for the Absorptive ND Filters? Kind regards, Rolf Loch

Reflective ND Filter Kits

  • Inconel Coated Ø25 mm SM1 Mounted Filters
  • NDK01 for 350 - 1100 nm Range
  • NUK01 Optimized for UV Operation Down to 200 nm
  • N-BK7 Reflective ND Filter With OD 1.3 Also Available (ND13A, Sold Separately)
  • UVFS Reflective ND Filter With OD 1.3 Also Available (NDUV13A, Sold Separately)
Item# Size Mount Included Storage Box Included Optical Densities
NDK01 Ø25 mm SM1 KT01 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1.0, 2.0, 3.0, 4.0
NUK01 Ø25 mm SM1 KT01 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
NDK01 Support Documentation
NDK01Box with 10 Reflective ND Filters, Ø25 mm, SM1 Mounted, 350 - 1100 nm
$675.24
Lead Time
NUK01 Support Documentation
NUK01Box with 10 UVFS Reflective Ø25 mm ND Filters, SM1-Mounted, 200 - 1200 nm
$699.05
Today

Absorptive ND Filter Kits

  • Comprehensive Set of Absorptive ND Filters
  • 400 - 650 nm Wavelength Range; For Performance at ≥650 nm, See Specs (Absorptive) Tab
  • 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
NEK02 Support Documentation
NEK02Box with 12 Absorptive Ø1/2" ND Filters, SM05-Mounted, 400 - 650 nm
$489.12
Today
NEK01 Support Documentation
NEK01Box with 10 Absorptive Ø25 mm ND Filters, SM1-Mounted, 400 - 650 nm
$564.86
Today
NEK03 Support Documentation
NEK03Box with 10 Absorptive Ø2" ND Filters, SM2-Mounted, 400 - 650 nm
$1,081.04
Today
NEK01S Support Documentation
NEK01SND Filter Set, 2 x 2 Square Filters, 10 pieces, 400 - 650 nm
$842.97
Today

Storage Boxes for Filters

  • Store and Organize Optics
  • Protect Optics from Damage
  • Foam Inserts Separate Optics
Item # Designed to Hold Max # of Filters
KT01 Mounted Ø1" (Ø25 mm) 10
KT06 Mounted Ø2" 10
KT03 Unmounted 2" x 2" 10
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
KT01 Support Documentation
KT01Storage Box for Mounted Ø1" (25 mm) Round Optics (Max. Capacity: 10)
$95.77
Today
KT06 Support Documentation
KT06Storage Box for Mounted Ø2" Round Optics (Max. Capacity: 10)
$95.77
Today
KT03 Support Documentation
KT03Storage Box for Unmounted 2" Square Optics (Max. Capacity: 10)
$90.09
Today
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