- Attenuate Light Within a Specific Wavelength Range
- Center Wavelengths from 405 nm to 1064 nm
- Ideal for Spectroscopy Applications
Transmission Direction Indicator
and Fiber Patch Cable
|Transmission in Passbands||Tavg > 90%|
|Peak Optical Density at Center Wavelength||>6.0|
|Clear Aperture||Ø21 mm|
|Center Wavelength Tolerance||±2 nm|
|Surface Quality||60-40 Scratch-Dig|
|Transmitted Wavefront Error (@ 633 nm)||<λ/2|
|Angle of Incidencea||0°|
|Front Surface Coating||Dielectric Stack|
|Back Surface Coating||AR Coated|
- Choose from 13 Center Wavelength Options
- Mounted in Ø25 mm Housing
- Peak Optical Density at Center Wavelength: >6.0 (T < 0.0001%)
- Dielectric Stack on Polished Glass Substrate
- Compatible with Thorlabs' Filter Mounts and Filter Wheels
- Select Notch Filters Available in Custom Sizes; Contact Tech Support for Details
Notch filters, also commonly referred to as band-stop or band-rejection filters, are designed to transmit most wavelengths with little intensity loss while attenuating light within a specific wavelength range (the stop band) to a very low level. They are essentially the inverse of bandpass filters, which offer high in-band transmission and high out-of-band rejection so as to only transmit light within a small wavelength range. See the Transmission Graphs and OD Graphs tabs for the performance over the passbands and blocking region.
Notch filters are useful in applications where one needs to block light from a laser. For instance, to obtain good signal-to-noise ratios in Raman spectroscopy experiments, it is critical that light from the pump laser be blocked. This is achieved by placing a notch filter in the detection channel of the setup. In addition to spectroscopy, notch filters are commonly used in laser-based fluorescence instrumentation and biomedical laser systems.
As with all dielectric stack filters, the transmission is dependent on the angle of incidence (AOI). The central wavelength of the blocking region will shift to shorter wavelengths as the AOI is increased. The AOI Graphs tab shows the transmission of s- and p-polarized light as a function of wavelength changes for different AOI.
Thorlabs' notch filters feature a dielectric coating on a polished glass substrate, which has excellent environmental durability. The dielectric stack provides high rejection through destructive interference and reflection in the stop band: the optical density is greater than 6.0 (corresponding to a transmission of less than 0.0001%) within the stop band. See the table below for available stop band center wavelengths. Regardless of the filter chosen, the transmitted beam's wavefront error for light at normal incidence will be less than λ/2 at 633 nm. These filters also have an AR coating on the back surface to ensure >90% average transmission within the passbands.
Each filter is housed in a black anodized aluminum ring that is labeled with an arrow indicating the design propagation direction. The ring makes handling easier and enhances the blocking OD by limiting scattering. These filters can be mounted in our extensive line of filter mounts and wheels. As the mounts are not threaded, Ø1" retaining rings will be required to mount the filters in one of our internally-threaded SM1 lens tubes. We do not recommend removing the filter from its mount as the risk of damaging the filter is very high. However, select filters are available unmounted as well as in custom sizes; contact Tech Support for more details.
Below are transmission plots for our notch filters, obtained at normal incidence. Although designed for use at normal incidence, the performance of these filters will not vary significantly if used within an AOI of ±3°, but the performance may differ slightly from that shown below. Please note that the measured data presented is typical, and performance may vary from lot to lot, especially outside of the specified wavelength range of each filter.
Our 633 nm filter (NF633-25) has a plot of the transmission as a function of the angle of incidence; this plot can be used as an example of how the center wavelength varies with AOI.
Plots of the optical density in the blocking region and spectra vs. AOI may be found on the OD Graphs and AOI Graphs tabs, respectively.
Click to Enlarge
Click for Angle of Incidence (AOI) Dependence Plot
Click Here for Raw Data for the 200 - 2600 nm Wavelength Range
The plots below detail the optical density in the blocking region of our notch filters. Please note that the measured data presented is typical, and performance may vary from lot to lot, especially outside of the specified wavelength range of each filter.
Plots of % transmission vs. wavelength and spectra vs. AOI may be found on the Transmission Graphs and AOI Graphs tabs, respectively.
Optical Density (OD) is related to transmission by the following relationship:
Click to Enlarge
Figure 1: Setup used to test notch filters. Light from the sources listed below were incident on a notch filter mounted on a rotation stage, and the spectra were recorded using Thorlabs' OSA201C Optical Spectrum Analyzer.
Modeling Off-Axis Performance: Optical Spectrum Analyzer Measurements
As the angle of incidence upon a thin-film interference filter increases, a phase shift will occur between each of the transmitted rays created from successive reflections within the filter. This will shift the filter's center wavelength downward, which can be modeled as:
where λ is the center wavelength at an incident angle of θ0, λ0 is the center wavelength at normal incidence, and n* is the effective index of refraction. The center wavelength shift of a multilayer interference filter can be characterized as equivalent to a monolayer with this effective index, which is between the high-index and low-index values for the thin films of the interference filter stack. The effective index can be experimentally determined from measurements of filter spectral transmission at various incident angles; the model is generally valid at small angles, but can work up to ~40° depending on the filter's structure. [1-2]
Measurements of filter transmission were made using the setup shown in Figure 1. The setup consisted of several Thorlabs' light sources (listed in the table under the Figure 1) in order to measure filters with center wavelengths ranging from 488 nm to 1064 nm. The spectral output from each filter was detected with our OSA201C optical spectrum analyzer. The filter was mounted in an LH1 adjustable lens mount mounted on an RP01 manual rotation stage in order to vary the AOI on the filter. Irises were used to control the beam size through the filter, and a half-wave plate was only used to maximize throughput.
Measurements were made of both S- and P-polarization states at AOI steps of 5° between 0° and 45°. All filters were tested except the NF405-13 filter, since a light source with a great enough power output at this wavelength was not available. The OSA software calculates the center wavelength from recorded spectra; these values were used to calculate the effective index n* using Equation 1.
The measured center wavelengths at each AOI are shown by clicking on the icons in the "OSA Measurements" column of the table below. Figures 2 and 3 show a summary of the results. In the graphs in the table, we also plot the theoretical curve based on the effective index for each filter; the value of n* used is the average of the values calculated at each AOI. The good agreement between the theoretical curve and the measured data points shows that the model can be used to determine the angle needed to achieve a particular center wavelength.
 Macleod, H.A, Thin-Film Optical Filters, 4th ed. Boca Raton: CRC Press, 2010.
 Pidgeon, C.R. and S.D. Smith, J. Opt. Soc. Am. 54, 1459 (1964).
Click to Enlarge
Figure 2: Plot showing the change in center wavelength from the on-axis value for various angles of incidence for S-Polarized light. These measurements were made using the setup shown in Figure 1.
Click to Enlarge
Figure 3: Plot showing the change in center wavelength from the on-axis value for various angles of incidence for P-Polarized light. These measurements were made using the setup shown in Figure 1.
Visualizing Spectral Performance: Spectrophotometer Measurements
Measurements were also taken using the spectrophotometer used to make the on-axis measurements shown on the Transmission Graphs tab. Transmission vs. wavelength plots for our notch filers, obtained at an AOI of 0°, 15°, 30°, and 45° for both S- and P-polarization states, can be found by clicking on the icons in the "Spectrophotometer Measurements" column of the table below. These measurements also show that the OD in the blocking region is decreased and the bandwidth is increased at higher AOI.
Plots of % transmission vs. wavelength and optical density in the blocking region may be found on the Transmission Graphs and OD Graphs tabs, respectively.
Please note: All measured data presented is an example of the performance of our notch filters. Performance will vary from filter to filter, especially at these off-axis angles of incidence that are not controlled during manufacturing.
|Item #||OSA Measurements
With Theoretical Curve
|Spectrophotometer Measurements||Calculated Effective Index (n*)a|
|S Polarization||P Polarization|
Aitana Cano  (posted 2023-04-11 15:11:50.09)
Good afternoon, I want to use a notch filter before entering the light in a fiber optics. I would like to know if there is any solution to assemble the filter and the fiber, so that all the light passes through the filter before entering the fiber. Thank you, Aitana Cano
cdolbashian  (posted 2023-04-13 10:49:15.0)
Thank you for reaching out to us with this application inquiry. I have reached out to you directly to discuss your application, experimental design, and potential solutions. For future application questions, please contact Techsupport@thorlabs.com.
Taeho Shin  (posted 2023-02-17 11:55:26.16)
Dear Sir, Hello. I am in the middle of building Raman spectrometer. As a light source, I am using your LMD785 laser. To block the 785 nm light entering the detector, I put your notch filter (NF785-33, OD~6) in front of the detector. But still significant light intensity is observed at the tail or wing. Even when I added one more the same notch filter expecting OD 12, the light at the tail position did not disappear at all. Is the your NF785 filter not additive? Is the LMD785 not proper for Raman applications? I need your help. Thanks. -- Taeho
cdolbashian  (posted 2023-04-03 01:59:14.0)
Thank you for reaching out to us Taeho. Nominally, OD values stack additively and your assumption should be correct. Without seeing your data, I cannot address a solution here. I have contacted you directly seeking more information.
Sara Vidal  (posted 2022-11-29 08:55:21.817)
Hello. We would like to know how we should proceed to clean the filter without damaging the coating. Thank you in advance.
cdolbashian  (posted 2022-12-02 03:57:29.0)
Thank you for reaching out to us with this inquiry. Following our general optics handling and cleaning guide should be sufficient: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=9025
Leonid Vyacheslavov  (posted 2020-02-28 01:12:17.66)
Dear technical support specialist, We bought two notch filters NF1064-44- Ø25 mm. Could you inform me the damage threshold for 1ms free running laser 1064 nm radiation for this filter. Thanks in advance. Leonid Vyacheslavov
llamb  (posted 2020-03-05 04:05:51.0)
Hello Leonid, thank you for contacting Thorlabs. We have not performed conclusive damage threshold testing for these filters yet. That being said, damage is highly dependent on whether the incident light is concentrated in the transmission or blocking region of the filter, so your beam size will have an impact. Nevertheless, preliminary data suggests that these filters should be able to withstand >10 J/cm^2 at 1064 nm (10 ns, 10 Hz), for reference.
John Linden  (posted 2019-12-02 02:29:30.287)
Can you manufacture a notch filter for 343nm wavelength? Thank you.
nbayconich  (posted 2019-12-05 09:28:28.0)
Thank you for contacting Thorlabs. I will reach out to you directly to discuss our custom capabilities.
user  (posted 2019-11-20 16:35:28.087)
There is no 355nm notch filter?! That is absurd!
nbayconich  (posted 2019-11-21 08:13:16.0)
Thank you for your feedback. At the moment we do not have plans to release a 355nm notch filter, I have posted your suggestion on our internal engineering forum.
Vincent Brooks  (posted 2019-06-12 11:37:15.863)
Hello, The transmission curve for the NF808-34 filter seems to show that the transmission at 780 is pretty good, however the states the lower pass band is only up to 778 nm. Please could you confirm if the transition at 780nm can be expected to be high? Thanks
YLohia  (posted 2019-06-12 03:00:04.0)
Hello, thank you for contacting Thorlabs. The spec is for an average transmission of >90% and is typical. The actual transmission band will vary from unit-to-unit. The raw data for the transmission (https://www.thorlabs.com/images/TabImages/NF808-34_data.xlsx) implies a typical throughput of 99.19% at 780nm.
jale.schneider  (posted 2018-08-28 09:58:39.51)
Dear Sir or Madam, do you have any data regarding the laser damage threshold of NF 1064-44? Thank you very much best regards Jale Schneider
YLohia  (posted 2018-08-29 12:18:01.0)
We have not performed conclusive damage threshold testing for these filters yet. That being said, damage is highly dependent on whether the incident light is concentrated in the transmission or blocking region of the filter. Nevertheless, preliminary data suggests that these filters should be able to withstand light with energy densities >10 J/cm^2 at 1064 nm (10 ns, 10 Hz).
Klaus.Bergner  (posted 2014-10-16 14:27:01.613)
Hi Thorlabs-Team, would it be possible to get a Notch filter for 1026nm (1030+-40nm or so)?
besembeson  (posted 2014-11-05 03:29:58.0)
Response from Bweh at Thorlabs USA: Yes we can provide this as a custom item for now. I will followup with you by email.
user  (posted 2014-01-16 23:31:14.647)
Hi support, I was wondering if you had a transmission graph for the 533 nm notch filter that extends into the 850 nm range?
jlow  (posted 2014-01-17 08:36:52.0)
Response from Jeremy at Thorlabs: The transmission scan data (from 200nm to 2600nm) can be found in the link under the graph or http://www.thorlabs.com/images/TabImages/NF533-17_Transmission.xlsx.
bob  (posted 2013-06-13 06:02:55.037)
Hello support, We were looking at notch coatings, like for example NF405-13. We were wondering if you can make similar passband coatings on our laser diodes. However, we would ask for coatings at 1550 nm, with a width of 15 nm. Thanks for your time, B. van Someren
tcohen  (posted 2013-06-13 12:50:00.0)
Response from Tim at Thorlabs: Thank you for your inquiry. We can offer many custom optics and I will contact you to discuss your requirements.
pf275  (posted 2013-06-04 05:36:23.63)
What is the transmisivity of the NF808-34 down to 400nm?
jlow  (posted 2013-06-04 10:10:00.0)
Response from Jeremy at Thorlabs: The NF808-34 transmission falls off rapidly below 600nm. At 400nm, the transmission will be close to 0%.
bdada  (posted 2011-10-25 13:30:00.0)
Response from Buki at Thorlabs: Thank you for your interest in Thorlabs products. We will contact you to discuss a discount and find out more about your specifications for the custom filter. Please contact TechSupport@thorlabs.com if you have further questions.
gustavo.demiguel  (posted 2011-10-25 03:22:49.0)
I am interested in purchasing the set of five notch filters but the price is quite high. would it be cheaper if I buy all together? Is there any possibility to design a filter with a narrower blocking peak, for example at 633 nm?
jjurado  (posted 2011-08-17 18:13:00.0)
Response from Javier at Thorlabs to charles.h.adams: We currently do not have concise damage threshold data for our notch filters, as the damage is highly dependent on whether the incident light is concentrated in the transmission or blocking region of the filter. Nevertheless, these filters should be able to withstand light intensities up to ~1W/cm^2.
charles.h.adams  (posted 2011-08-17 11:12:03.0)
What is the damage threshold for the NF1064-44 and NF533-17? Would these be appropriate for use with a nanosecond laser capable of, tens of mW/cm^2?
jjurado  (posted 2011-04-04 11:53:00.0)
Response from Javier at Thorlabs to Konstanze: Thank you very much for contacting us. The transmission of the NF1064-44 notch filter at 532 nm is close to 0%, so it is not suitable for your application. The FL532-10 filter would be a better match; however, at 2 W, you will most likely exceed the damage threshold of the filter, especially if the diameter of the beam is small. If possible, I would recommend attenuating the output from your laser. I will contact you directly for further support.
k.hild  (posted 2011-04-04 11:19:20.0)
I am interested in the notch filter to cut out the 1064 laser line. On the data sheet and in the specification it says that the transmission band starts at 800nm. I was assuming that the transmission is quite close to 100% for other wavelengths as well, but this is obviously not stated, so could you tell me what the transmission of the NF1064-44 Support Documentation NF1064-44 - Notch Filter, CWL = 1064 nm, FWHM = 44 nm filter is at 532nm (I want to use it to get most of the energy from at 532nm out of the laser but block the also produced 1064. I had also considered using a laser line filter: FL532-10 Support Documentation FL532-10 - Laser Line Filter, CWL=532 ± 2 nm, FWHM=10 ± 2 nm , but this one only lets 80% of the light through at the lasing line. As I am using a relative powerful laser (up to 2W)I am not sure I want that much heat dissapated in my filter. Regards, Konstanze
tor  (posted 2010-11-19 16:28:53.0)
Response from Tor at Thorlabs to kmcao: We may be able to provide custom dimensions. I will contact you directly for your specific requirements.
kmcao  (posted 2010-11-19 15:26:17.0)
the size can be larger as over 50mm?
Thorlabs  (posted 2010-11-08 10:38:16.0)
Response from Javier at Thorlabs to jcogger: in these notch filters, the rejected wavelength band is blocked through a combination of destructive interference and reflection, the level of which varies from filter to filter. I will contact you directly with pricing information and to follow up on your technical inquiry.
jcogger  (posted 2010-11-08 09:40:34.0)
Do these notch filters reflect or absorb the the blocked wavelength? What is quantity pricing? I would like to design these filters into my product but the piece price makes it prohibitive.