N-BK7 Diffuse Reflectors, Protected Gold Coating

  • Highly Diffusive in the IR Spectral Region
  • Polished for Greater Uniformity than Sand Blasting
  • Offered in 120, 220, 600, or 1500 Grit Polishes


600 Grit


120 Grit


1500 Grit

DG10-1500-M01 Reflecting
Collimated Light from a
L808P200 Laser Diode
Housed in an LDM21 Mount

Related Items

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Diffuser Selection Guide
Ground Glass Diffusers
Standard Diffusers N-BK7 Substrate Unmounted, Uncoated 350 nm to 2.0 µm
Unmounted, AR Coated 350 nm - 700 nm
650 nm - 1050 nm
Mounted, Uncoated 350 nm - 2.0 µm
UVFS Substrate Unmounted, Uncoated 185 nm - 2.0 µm
Diffuse Reflectors N-BK7 Substrate Unmounted, UV-Enhanced Aluminum Coated 250 nm - 450 nm
Unmounted, Protected Silver Coated 450 nm - 20 µm
Unmounted, Protected Gold Coated 800 nm - 20 µm
Alignment Disks
Engineered Diffusers
Diffuser Kits
Optical Coatings and Substrates


  • Ø1" Diffuse Reflectors
  • Coated Surface has 120, 220, 600, or 1500 Grit
  • Protected Gold HR Coating for the 800 nm to 20 µm Range
  • Near-Gaussian Intensity Pattern at Small Angles of Incidence (AOIs) (See Graph Below)
  • Clear Aperture: >90% Diameter

Thorlabs' Diffuse Reflectors are a solution for applications requiring a diffuse intensity pattern. The diffuse reflectors on this page have a protected gold coating deposited on the ground side of the optic. Unlike transmissive diffusers, these reflective diffusers are not susceptible to absorption losses and thus achieve >96% average reflectance in the 800 nm to 20 µm range. For other coating options, please see the diffuser selection guide to the right. These diffuse reflectors are produced from an N-BK7 substrate and are available in 120, 220, 600, and 1500 grit polishes.

Polished diffusers are advantageous over sand blasted diffusers as the surface has greater uniformity. The various grits provide a range of reflected intensity distributions. A coarser grind (e.g., 120) creates a wider diffusion pattern, while a finer grind (e.g., 1500) will provide a more localized one. The distribution of reflected light (AOI = 0°) for each diffuser is shown in the graph below. To see how the distribution changes for AOIs of 15°, 30°, and 45°, see the Graphs tab. This sample data is typical and results may vary.

These diffuse reflectors have a thickness of 2.0 mm and thus are too thin to be used in our standard mirror mounts. Mounting options include our LMR1 Fixed Mount for Ø1" Optics, Ø1" lens tubes, or the KM100T Threaded Kinematic Mount. When mounting a diffuse reflector in a threaded optic mount, such as the LMR1, the ground and coated surface should face the lip of the mount and the retaining ring should secure the uncoated side, as shown in the image on the bottom right. If the diffuse reflector is mounted facing the opposite direction, the reflective face will be recessed inside the mount and the housing will block a portion of the diffusely reflected light.

Click to Enlarge

Mount the optic with the input face towards the back of the LMR1 to prevent the obstruction of reflected beams.

Click to Enlarge

Click Here for Raw Data
This typical data was taken with a light source at a 0° AOI. The curves are normalized to the peak measured value for the 1500 grit diffuser to highlight the differences in peak shape and intensity distribution between diffusers.
Common Specifications
Coating on Grit Side Protected Gold
Average Reflectance of Coating
(AOI = 0 to 45°)
>96% from 800 nm to 20 µm
Substrate N-BK7
Diameter 1.00" (25.4 mm)
Thickness 2.0 mm (0.08")
Clear Aperture >90% Diameter
Parallelism <3 arcmin
Item # Grit
DG10-120-M01 120
DG10-220-M01 220
DG10-600-M01 600
DG10-1500-M01 1500

Below are the reflectance curves for the protected gold coating for S-polarized, P-polarized, and unpolarized light. A link to download the raw data is available below the graph. The shaded regions in the graphs denote the ranges over which we recommend using these diffuse reflectors. Please note that the reflectance outside of these bands is not as rigorously monitored in quality control, and can vary from lot to lot, especially in out-of-band regions where the reflectance is fluctuating or sloped.

Protected Gold at Near-Normal Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for Protected Gold
Protected Gold at 45 Degree Incident Angle
Click to Enlarge

Excel Spreadsheet with Raw Data for Protected Gold


For each grit available on this page, we have provided data showing the reflected intensity distribution for four AOIs. Intensity distributions were measured with a collimated source at a 0°, 15°, 30°, or 45° AOI. The gap in each curve represents the AOI of the light source. The intensity measurements were normalized by setting the peak measured value for the 1500 grit diffuser with the source at a 0° AOI equal to 1.

Intensity Distributions for 120 Grit Diffusers
Click to Enlarge

Click Here for Raw Data
Intensity Distributions for 220 Grit Diffusers
Click to Enlarge

Click Here for Raw Data
Intensity Distributions for 600 Grit Diffusers
Click to Enlarge

Click Here for Raw Data
Intensity Distributions for 1500 Grit Diffusers
Click to Enlarge

Click Here for Raw Data

Posted Comments:
隆之 島  (posted 2023-07-05 14:53:30.657)
ご担当者様  産業技術総合研究所の島と申します。  DG10-220-M01を5点購入させて頂きました。  うち1点が本日納品されました。  拡散板の表面を見たところ、一部金属光沢のある  箇所があり、表面がやや不均一な状態となって  いました。  状況お知らせしておきます。  宜しくお願い致します。
cdolbashian  (posted 2023-07-06 08:55:49.0)
Thank you for reaching out to us with this feedback. Our local team in Japan has reached out to you to discuss your inquiry. For future tech support inquiries, please feel free to contact your local office: sales@thorlabs.jp and they will connect you with a support specialist.
Joris Baraillon  (posted 2022-12-19 15:32:13.223)
Dear Thorlabs team, I have three questions concerning the gold diffusers. We already have the 4 diffusers in our lab. First question : Have you tested the influence of the source wavelength (in the mid-IR, between 3 and 12 µm) on the intensity distribution of the gold diffusers (DG10-120 to DG10-1500) ? I expect the diffusing efficiency to be strongly dependent on the wavelength, especially for the smallest grit size (#1500). Second question: could you confirm that the grit sizes are the following ?: #120 : 109µm #220 : 58µm #600 : 9.3µm #1500 : 2.0µm Last question: do you have more details on the geometrical and optical characteristics of the diffuseurs (such as the correlation length) ? I thank you in advance for your answer. Best regards, Joris Baraillon
cdolbashian  (posted 2023-01-10 03:16:09.0)
Thank you for reaching out to us with this inquiry Joris. I have some answers below. 1. We have not explicitly tested this, though we would tend to agree with you. 2. We cannot confirm this as we do not measure the specific size of the particles, and the standard we use is not always the same throughout the years. We characterize them by the grit # and the performance. 3. We do not have this data to share.
Richard Staehr  (posted 2021-05-03 06:48:27.18)
Dear Thorlabs Team, I'm interested in a DG10-220-M01. Is it possible to get such a protected gold coated diffuse reflector in square shape (similar to DG100X100-220, maybe even different sizes)? You can reach out to me via Email. Thanks, Richard
YLohia  (posted 2021-05-03 01:45:08.0)
Hello Richard, thank you for contacting Thorlabs. Custom optics can be requested by clicking on the "Request Quote" button above or by emailing your local Thorlabs Tech Support team (in your case, europe@thorlabs.com). We will discuss the possibility of offering this directly.
Heinz Falk  (posted 2019-03-18 07:52:49.31)
Hello, we are using the DG10-220-M01 for calibrating a reflectometer. In your specification one finds the reflected intensity to be 94%. Does this mean, that the total reflected intensity observed in the half sphere amounts to 94% of the incident intensity? In this case, the intensity distribution at 0° AOI cannot hold for all grids. Thank you for a clarification.
nbayconich  (posted 2019-04-15 10:38:22.0)
Thank you for your feedback regarding our DG10-220-M01 gold coated ground glass diffusers. Regarding your question about the reflected intensity would it be possible to clarify what you mean by the reflected intensity observed in the half sphere and where you found the reflected intensity to be 94%? The 12 degree and 45 degree reflectance vs. wavelength plots are assuming a gold coated plano surface mirror with an incident source at either 12 or 45 degrees AOI. The Intensity distribution plots refer to the relative intensity measured on the actual gold coated reflective diffusers. All plots are normalized by setting the peak measured value for the 1500 grit diffuser with the source at 0 degrees AOI equal to 1.
hoerner.thomas  (posted 2018-02-05 12:31:07.7)
Dear Thorlabs Team, I'm interested in a DG10-1500-M01 gold reflective ground glass diffuser, 1500 Grit. Is it possible to get such a diffuser with unprotected gold coating instead of protected gold? Could you contact me with a corresponding quotation? Thanks Thomas
nbayconich  (posted 2018-02-06 03:38:45.0)
Thank you for contacting Thorlabs. Yes we can provide these diffusers with un-protected gold coating. A techsupport representative will reach out to you directly with a quote.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
DG10-120-M01 Support Documentation
DG10-120-M01Ø1" Protected Gold Reflective Ground Glass Diffuser, 120 Grit
DG10-220-M01 Support Documentation
DG10-220-M01Ø1" Protected Gold Reflective Ground Glass Diffuser, 220 Grit
DG10-600-M01 Support Documentation
DG10-600-M01Ø1" Protected Gold Reflective Ground Glass Diffuser, 600 Grit
DG10-1500-M01 Support Documentation
DG10-1500-M01Ø1" Protected Gold Reflective Ground Glass Diffuser, 1500 Grit
Last Edited: Jul 25, 2013 Author: Lori Stover