What Wavelengths Can Magnesium Fluoride Transmit?

Magnesium fluoride (MgF₂) transmits a broad range of ultraviolet, visible, and infrared light. As a practical starting point, optical-grade MgF₂ is commonly specified for transmission from approximately 0.12 μm (120 nm) to 7 μm, although the usable range depends on material quality, crystal form, thickness, surface finish, and measurement conditions. Some specialized material may transmit at shorter ultraviolet wavelengths, while performance near either end of the range requires confirmation against the supplier’s data for the exact component.

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For a design decision, I recommend treating these figures as an approximate material range—not a guarantee that a finished window or lens will meet a particular transmission percentage at every wavelength. Surface reflections, coatings, incidence angle, and polarization can all affect measured throughput. Below, I explain how to apply the range to optical selection and what information to confirm before ordering.

Quick Summary: MgF₂ Transmission Range

• Approximate broad range: 0.12–7 μm for many optical-grade applications.
• Ultraviolet use: MgF₂ is selected for UV optics, including applications where ordinary optical glasses may not transmit adequately.
• Visible use: It transmits visible light and is commonly used as a coating material to reduce reflection.
• Infrared use: It can serve in some near- and mid-infrared applications, but transmission near the long-wavelength limit should be checked for the required thickness and component.
• Buyer priority: Specify the wavelength interval, required transmission, thickness, optical form, and operating conditions—not just “UV to IR.”

What Determines the Usable Wavelength Range?

Material absorption and wavelength limits

Transmission describes how much incident light passes through a material at a given wavelength. MgF₂ has a wide optical window, but its transmission is not uniform across that window. Absorption increases near the material’s short- and long-wavelength limits, so a part intended for a narrow band near an edge needs more careful verification than one designed for visible light.

Published ranges can differ because they may refer to different material grades, sample thicknesses, surface conditions, or transmission thresholds. A stated limit may describe detectable transmission rather than the level required for a high-efficiency optical system. I therefore recommend using the approximate 0.12–7 μm range for initial screening, then requesting data for the actual material and geometry.

Thickness, surfaces, and system losses

A thicker component generally gives light a longer path through the material, which can increase the effect of bulk absorption. Uncoated surfaces also reflect some incident light, and that reflection can reduce total transmission even where the bulk material itself absorbs little. As a result, a material’s transmission curve and a finished part’s measured throughput are not interchangeable.

Coatings can change surface reflection, but they must be designed for the intended wavelength band and operating conditions. A coating optimized for visible light should not be assumed to perform similarly in the deep ultraviolet or infrared. Include coating requirements in the inquiry if the optical component will be used in a system with a defined throughput target.

Where MgF₂ Fits Across the Spectrum

Ultraviolet applications

MgF₂ is a useful candidate for UV windows, lenses, and other optical components because it can transmit into the ultraviolet region. The exact short-wavelength performance is particularly sensitive to material quality, thickness, surface finish, and contamination. For deep-UV applications, buyers should identify the minimum wavelength explicitly and request confirmation for the proposed grade and part.

UV designs also need to account for exposure conditions. Intense sources, vacuum or controlled atmospheres, cleaning methods, and surface contamination may affect service performance even when the material’s nominal transmission range is suitable. These system-level details should be reviewed alongside the wavelength specification.

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Visible-light applications

MgF₂ transmits visible light and has an approximate refractive index of 1.38–1.39 near 589 nm, depending on crystal orientation and polarization. This relatively low refractive index is one reason MgF₂ is widely used as a thin-film material in antireflection coatings. In a coating, the optical behavior depends on film thickness and the substrate beneath it, so coating performance should be specified for the complete optical assembly.

For a visible-light window or lens, consider the required spectral band, surface quality, component dimensions, and whether polarization effects matter. MgF₂ is birefringent, meaning its optical response differs with crystal direction. That property may be relevant in polarization-sensitive designs and should be discussed when specifying single-crystal components.

Infrared applications

MgF₂ can be considered for selected near- and mid-infrared applications, with a commonly cited upper transmission limit around 7 μm. The long-wavelength edge is not a universal cutoff for every grade or test setup, and transmission can decline as the material approaches its absorption region. If the design operates near this limit, ask for wavelength-specific data rather than relying on a broad catalog range.

For infrared service, also confirm the operating temperature, incidence angle, polarization, and environmental conditions. A component that is suitable at room temperature and normal incidence may not match a system with different conditions. When transmission requirements are stringent, evaluate the full optical path, including coatings and any protective layers.

Key Specifications to Confirm Before Ordering

Common Buyer Mistakes

• Using “UV-transparent” as the full requirement: State the actual minimum wavelength and required transmission.
• Assuming the material range equals component performance: Confirm how the supplier defines and measures transmission for the finished part.
• Ignoring thickness: Request data or evaluation for the intended thickness, especially near a transmission limit.
• Overlooking polarization and orientation: For sensitive optical systems, state whether birefringence could affect the design.
• Leaving coatings until later: Coating selection can change reflection losses and should be aligned with the operating band.

How to Assess MgF₂ for Your Application

Use a wavelength-led selection process

1. Define the operating band. Provide the full wavelength interval and identify any critical wavelengths within it.
2. Set measurable performance targets. Specify the required transmission and clarify whether it applies to the bare material or finished component.
3. Describe the part. Share the thickness, dimensions, tolerances, surface requirements, and preferred material form.
4. Document operating conditions. Include temperature, incidence angle, polarization, atmosphere, and exposure conditions when relevant.
5. Review supplier documentation. Compare the proposed grade and component data with the actual design requirements before approving production.

This process helps distinguish a suitable material from a suitable finished optical component. It also gives suppliers enough detail to identify where additional testing, a different grade, or a coating may be needed. If the intended band is near 0.12 μm or 7 μm, make that boundary explicit in the first inquiry.

Working with Azeal Materials

At Azeal Materials, we support B2B buyers evaluating magnesium fluoride for optical material and component requirements. To help us assess fit, share your wavelength range, target transmission, dimensions, thickness, surface or coating needs, and operating environment. We can then discuss the relevant material options and the documentation needed to confirm suitability for your application.

Conclusion

Magnesium fluoride can transmit ultraviolet, visible, and infrared light over an approximate range of 0.12–7 μm, with actual performance depending on grade, thickness, surfaces, and test conditions. The practical answer is not simply whether MgF₂ covers a wavelength, but whether the specific finished part meets your transmission target across the required band. For your next step, prepare the wavelength interval and component specifications, then request application-specific confirmation from your supplier before finalizing the design.

Contact us to discuss your requirements of What Wavelengths Can Magnesium Fluoride Transmit?. Our experienced sales team can help you identify the options that best suit your needs.