Exceptional Spectral Range
Useful transmission from approximately 0.11 to 7.5 µm, depending on optical grade, thickness, surface finish, and coating.
Optical Fluoride Crystal
Magnesium Fluoride (MgF₂)
Durable UV-to-Infrared Performance for Precision Optical Systems.
A durable uniaxial fluoride crystal offering strong ultraviolet-to-infrared transmission, low refractive index, and excellent environmental resistance for spectroscopy, laser, polarization, and space-optics applications.
Why Magnesium Fluoride
A Durable Fluoride Crystal for UV, Visible, and Infrared Optics
Magnesium fluoride combines broad spectral transmission with excellent chemical resistance, low refractive index, and good thermal durability. It is widely selected for UV windows, polarization optics, spectroscopy, space systems, and durable protective optical components.
Low Refractive Index
Low index reduces uncoated Fresnel reflection and supports high transmission across broad wavelength bands.
Low Dispersion
Low refractive index and useful dispersion characteristics support broadband optical and polarization designs.
Low Stress Birefringence
MgF₂ is a uniaxial birefringent crystal, making orientation important for polarization-sensitive designs.
Engineering Properties
Optical, Mechanical, and Thermal Characteristics
Representative values for optical-grade magnesium fluoride. Final values vary by crystal grade, wavelength, orientation, thickness, supplier specification, and test method.
Physical & Mechanical Properties
| Chemical Formula | MgF₂ |
|---|---|
| Crystal Structure | Tetragonal, uniaxial fluorite structure |
| Density | Approximately 3.15 g/cm³ |
| Knoop Hardness | Approximately 415 |
| Young’s Modulus | Approximately 138 GPa |
| Poisson’s Ratio | Approximately 0.27 |
| Thermal Expansion | Anisotropic; approximately 9–14 × 10⁻⁶/K depending on crystal axis |
| Melting Point | Approximately 1261°C |
Optical Properties
| Transmission Range | Approximately 0.11–7.5 µm, orientation, grade, and thickness dependent |
|---|---|
| Refractive Index nd | Approximately 1.38 |
| Abbe Number Vd | Approximately 106 |
| Birefringence | Uniaxial birefringent crystal; orientation should be specified for polarization-sensitive designs |
| Reflection Loss | Low relative to many optical materials due to low refractive index |
| Coating Compatibility | UV, VIS, NIR, MWIR AR, beamsplitter, and custom coatings |
| Available Grades | VUV, UV, optical, polarization, and infrared grades |
Optical Transmission
Broad Transmission from Vacuum UV to Mid-Infrared
MgF₂ provides broad spectral performance and strong environmental durability. Actual transmission depends on crystal orientation, grade, thickness, surface condition, and coating design.
Representative only. Final transmission depends on grade, thickness, surface finish, absorption bands, and coating.
Material Comparison
When Magnesium Fluoride Is the Best Fit
| Property | Sapphire | BK7 | Fused Silica | MgF₂ |
|---|---|---|---|---|
| Deep-UV Performance | Very Good | Limited | Excellent | Excellent |
| Infrared Reach | Good | Limited | Limited | Excellent |
| Chromatic Dispersion | Moderate | Low | Low | Very Low |
| Scratch Resistance | Excellent | Moderate | Good | Low |
| Thermal Expansion | Low | Moderate | Very Low | Higher |
Manufacturing Capabilities
From MgF₂ Crystal Blank to Finished Optical Component
COE Sapphire supports prototype, low-volume, and repeat production of precision magnesium fluoride optics with controlled fabrication, coating, and inspection.
Precision Machining
Controlled cutting, edging, beveling, drilling, and custom geometry fabrication for an anisotropic optical crystal.
Optical Polishing
Precision flat, spherical, and custom polishing with process control to control surface quality, crystal orientation, and edge integrity.
Optical Coating
UV, visible, NIR, MWIR AR, beamsplitter, and application-specific multilayer coatings.
Quality Assurance
Dimensional inspection, interferometry, surface inspection, transmission verification, and documentation.
Design Guide
Specify the Right Magnesium Fluoride Optical Component
Provide optical grade, operating wavelength, dimensions, tolerances, surface quality, flatness or power, wedge or parallelism, clear aperture, edge treatment, coating, quantity, and environmental requirements.
Discuss Your SpecificationMaterial GradeVUV, UV, polarization, optical, or IR grade
Surface QualityCommercial through precision optical grades
Flatness / PowerApplication-specific interferometric control
Wedge / ParallelismPrecision parallel, wedged, or custom geometry
Edge TreatmentProtective bevel or chamfer recommended for fragile edges
CoatingsUV, VIS, NIR, MWIR, beamsplitter, and custom coatings
Related Optical Components
Magnesium Fluoride Components Manufactured to Your Specification
Frequently Asked Questions
Magnesium Fluoride FAQ
What is magnesium fluoride commonly used for?
MgF₂ is widely used for UV windows, polarization optics, spectroscopy, durable protective windows, space optics, and broadband anti-reflection systems.
What wavelength range can MgF₂ transmit?
High-quality magnesium fluoride can provide useful transmission from the deep ultraviolet into the infrared, commonly cited at approximately 0.11–7.5 µm depending on grade and thickness.
How does magnesium fluoride compare with fused silica?
Both materials provide strong UV performance. MgF₂ extends farther into the infrared and has lower dispersion, while fused silica is generally tougher, has far lower thermal expansion, and is easier to process.
Is magnesium fluoride birefringent?
MgF₂ is naturally birefringent because of its uniaxial crystal structure. Crystal orientation should be specified for polarization-sensitive applications.
Does magnesium fluoride require special handling?
Yes. MgF₂ is harder and more environmentally durable than many fluoride crystals, but crystal orientation and edge design still require care, so protective edge design, clean handling, careful mounting, and controlled cleaning are recommended.
Can magnesium fluoride be optically coated?
Yes. MgF₂ is compatible with UV, visible, near-infrared, mid-infrared, beamsplitter, and custom multilayer coatings when coating design and process conditions are matched to the substrate.
Can COE Sapphire manufacture custom MgF₂ shapes and tolerances?
Yes. COE Sapphire can manufacture custom windows, lenses, prisms, wedges, apertures, holes, edge treatments, and application-specific tolerances.
What information is needed for a MgF₂ quotation?
Please provide material grade, wavelength range, dimensions, tolerances, surface quality, flatness or power, wedge or parallelism, clear aperture, coating, quantity, and inspection requirements.
Custom Magnesium Fluoride Optical Components
Request a QuoteReady to Discuss Your MgF₂ Project?
Send us your drawing, specification, or application requirements.