Products Home / Optical Elements / Optical Filters / Neutral Density Filters / Neutral Density Filters: Absorptive/Reflective / ND Filters: Unmounted, AR Coated for 350 - 700 nmND Filters: Unmounted, AR Coated for 350 - 700 nm
- Ø1/2" and Ø25 mm Versions Available
- Optical Densities Ranging from 0.1 to 6.0
- Ideal for Low-Power Applications (<1 W)
NE50B-A
(Ø25 mm)
NE520B-A
(Ø1/2")
Application Idea
NE505B-A Mounted in LMR05
Please Wait
| Neutral Density Filter Selection Guide | |
|---|---|
| Absorptive | |
| Uncoated (400 - 650 nm) |
Mounted |
| Unmounted | |
| Uncoated (1000 - 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 | |
| Variable | |
| Reflective | |
| UV Fused Silica (200 - 1200 nm) |
Mounted |
| Unmounted | |
| N-BK7 (350 - 1100 nm) |
Mounted |
| Unmounted | |
| ZnSe (2 - 16 µm) |
Mounted |
| Unmounted | |
| Wedged UVFS (200 - 1200 nm) | |
| Wedged N-BK7 (350 - 1100 nm) | |
| Wedged ZnSe (2 - 16 µm) | |
| Variable | |
| Neutral Density Filter Kits | |
Click to Enlarge
One of Our Electron Beam Deposition Chambers that is Used to Coat Neutral Density Filters
Features
- Attenuate Light in the Visible (350 - 700 nm AR Coating)
- Optical Densities at 633 nm Prior to Coating from 0.1 to 6.0
- Unmounted Ø1/2" and Ø25 mm Versions
- AR Coated to Reduce Back Reflections in an Optical System
- Ideal for Low-Power Applications (<1 Watt)
Thorlabs is pleased to offer its most popular unmounted absorptive neutral density filters with a broadband antireflection coating for the 350 - 700 nm range deposited on both surfaces. These filters are also available in mounted versions or with a broadband AR coating for the 650 - 1050 nm range. Please see the Selection Guide to the right for more information.
The high-performance, multilayer broadband A coating deposited on each filter is designed to minimize surface reflections within the 350 - 700 nm range, thereby reducing the amount of stray light present. These coatings provide an average reflectance that is less than 0.5% per surface over the specified wavelength range when light is normally incident on the filter surface. Typical transmission data is shown by clicking on the blue info icons (
) in the tables below.
Unlike metallic neutral density filters, each absorptive ND filter is fabricated from one member of a family of Schott glasses (see the Specs tab for more information). Each Schott glass has a spectrally flat absorption coefficient. By varying the type of glass used and the thickness of that glass, we are able to produce our entire line of absorptive ND filters from just four types of Schott glass. See below for detailed information about the average transmission obtained with each of our AR-coated absorptive neutral density filters.
Optical Density and Transmission
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
where T is a value between 0 and 1. Choosing an ND filter with a higher optical density will translate to lower transmission and greater absorption of the incident light. For higher transmission and less absorption, a lower optical density would be appropriate. 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 (%).
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.
| Optical Density (OD)a |
OD Tolerancea |
Substrate | Substrate Thicknessb |
Ø1/2" Item # |
Ø25 mm Item # |
|---|---|---|---|---|---|
| 0.1 | ±0.01 | NG11 | 0.6 mm | NE501B-A | NE01B-B |
| 0.2 | ±0.01 | NG11 | 1.4 mm | NE502B-A | NE02B-B |
| 0.3 | ±0.015 | NG11 | 2.3 mm | NE503B-A | NE03B-B |
| 0.4 | ±0.02 | NG4 | 0.7 mm | NE504B-A | NE04B-B |
| 0.5 | ±0.025 | NG4 | 0.9 mm | NE505B-A | NE05B-B |
| 0.6 | ±0.03 | NG4 | 1.1 mm | NE506B-A | NE06B-B |
| 0.7 | ±0.04 | NG4 | 1.3 mm | NE507B-A | NE07B-B |
| 0.8 | ±0.05 | NG4 | 1.5 mm | NE508B-A | NE08B-B |
| 0.9 | ±0.05 | NG4 | 1.7 mm | NE509B-A | NE09B-B |
| 1.0 | ±0.05 | NG4 | 1.9 mm | NE510B-A | NE10B-B |
| 1.3 | ±0.065 | NG4 | 2.5 mm | NE513B-A | NE13B-B |
| 1.5 | ±0.08 | NG4 | 2.9 mm | NE515B-A | NE15B-B |
| 2.0 | ±0.1 | NG9 | 1.4 mm | NE520B-A | NE20B-B |
| 3.0 | ±0.15 | NG9 | 2.1 mm | NE530B-A | NE30B-B |
| 4.0 | ±0.2 | NG9 | 2.8 mm | NE540B-A | NE40B-B |
| 5.0 | ±0.25 | NG9 | 3.6 mm | NE550B-A | NE50B-B |
| 6.0 | ±0.3 | NG1 | 1.5 mm | NE560B-A | NE60B-B |
| General Specifications | ||
|---|---|---|
| Diameter | 12.7 mm | 25.0 mm |
| Diameter Tolerance | +0.00 / -0.25 mm | |
| Clear Aperture | >Ø11.43 mm | >Ø20.0 mm |
| AR Coating Range | 350 - 700 nm | |
| Reflectance (Average) | <0.5% per Surfacea | |
| Surface Quality | 60-40 Scratch-Dig | |
| Parallelism | <10 arcsec | |
| For OD < 1.3 | ||
| Transmitted Wavefront Error (TWE) | <λ/4 (@ 633 nm) | <λ/4 (@ 633 nm) |
| For OD ≥ 1.3 | ||
| Surface Flatness | <λ/4 (@ 633 nm) | - |
| Transmitted Wavefront Error (TWE) | - | <λ/4 (@ 633 nm) |
Click to Enlarge
Click Here for Raw Data
The blue shaded region indicates the specified 350 - 700 nm wavelength range for optimum performance.
The shaded regions in the graphs below denote the wavelength range for which the AR coating performance is specified. Click here to download optical density and transmission data. For the transmission and optical density of a particular filter, please click in the row corresponding to the filter in the tables below.
Click to Enlarge
Click Here for Raw Data
The blue shaded region indicates the specified 350 - 700 nm wavelength range for optimum performance.
| Posted Comments: | |
Paul Taylor
(posted 2024-03-23 09:55:29.497) I have an application where the ND filter would be absorbing approx 60% of a 0.4W beam at 355nm, diameter 4mm, pulsed 10ns at 40kHz.
The duty cycle is approx 50% with the on time being approx 3 seconds.
I would need 100 pieces
Would you recommend this type of part for long life use (multiple years running 24/7? jdelia
(posted 2024-04-03 09:23:48.0) Thank you for contacting Thorlabs. We unfortunately have not tested these filters under "multiple years running 24/7" conditions, nor have we tested at 355 nm. I have reached out to you directly to discuss your application. Lauri K
(posted 2021-04-21 11:12:54.55) Do you have any damage threshold data on these filters, especially NE501B-A with pulsed lasers at VIS range? cdolbashian
(posted 2021-04-27 10:45:06.0) Thank you for contacting ThorLabs. When considering the potential for laser induced damage on our optics, it is important to know all of the parameters of your laser: Pulse duration, wavelength, repetition rate, and beam diameter.
You have shared with me the following specs: Wavelength-532nm, pulse width-400ps, repetition rate-1MHz, e^-2 diameter-1mm.
Although we have not tested these components a laser with these specifications ourselves, we expect this to be fine for your laser parameters. That being said, we cannot provide guarantees for this due to the lack of formal damage threshold testing for these optics. n house
(posted 2019-04-16 18:55:24.933) I recently purchased these unmounted AR-coated ND filters. Are the OD plots you show on your website the plots I should expect, or can the intensity of transmission change slightly from batch-to-batch? YLohia
(posted 2019-04-17 09:08:16.0) Hello, thank you for contacting Thorlabs. The plots shown on the website are typical, so there would be a slight batch-to-batch variation over the specified operating range. Since these are AR-coated, there may be more significant variations in the out-of-band regions between different batches. gilliss
(posted 2017-02-22 12:26:04.373) Looking at plots such as
https://www.thorlabs.com/images/TabImages/ND_Filters_A-Coated_Optical_Density_All_780.gif
and then
https://www.thorlabs.com/images/TabImages/ND_Filters_A-Coated_Optical_Density_Rest_780.gif
I'm confused as to why all of the features in ND2.0 filters and up seem to shift over by 50nm. Could this be a measurement error? By these plots, all filters below OD2.0 seem appropriate for the stated wavelength range of 350 to 700, but the higher ones seem to only be useful above 400 nm. jlow
(posted 2017-03-01 04:46:47.0) Response from Jeremy at Thorlabs: The reason there's a shift is because of the material used. The ND filters with OD2, 3, 4, and 5, are made from NG9 glass whereas the lower OD filters were made with NG4 or NG11 glass. You can see the type of glass used under the Specs tab. michele.maiorano
(posted 2015-01-12 09:39:41.34) Dear Sirs,
I would like to buy about 30 unmounted and AR-coated absorptive ND filters for both visible and NIR light at different OD, but I need bigger sizes, i.e. 37.0 +0.0/-0.2 mm: could it be possible to make such an order?
Thank you for your attention.
Best regards,
Michele Maiorano besembeson
(posted 2015-01-13 06:36:05.0) Response from Bweh at Thorlabs: Yes we do provide custom sizes for these ND filters. I will followup with you by email for your OD, AR coating specifications and quotation. |
Unmounted Absorptive ND Filters (A Coated)