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Custom Magnesium Fluoride

Sapphire windows for Energy, Utilities and RenewablesMagnesium Fluoride (MgF2) is a colourless and durable crystalline material grown by vacuum Stockbarger technique. Whilst magnesium fluoride does transmit into the MWIR region, its transmission is inferior compared to calcium fluoride and barium fluoride, therefore its main applications fall into the VUV and UV regions.
It exhibits many beneficial properties including:

  • Naturally birefringent
  • Resistant to mechanical shock
  • Low absorption
  • Chemically stable
  • Resistant to water
  • Resistant to thermal shock

Below is a brief summary of magnesium fluoride’s optical properties, a full data sheet is available here.

Transmission range

0.12 to 7µm

Refractive Index

1.413 @ 0.22µm


3.18 g/cm3

Melting Point



Knoop 415

Knight Optical supplies high quality magnesium fluoride components, including windows, lenses and prisms, made to your custom specification. We can offer uncoated and coated optics, including broadband antireflective (BBAR) coatings. Our typical manufacturing specifications are listed below however we are always expanding our capabilities so if your requirements are not mentioned below, please contact our technical sales team who will guide you through your enquiry.


< 5mm to 50mm +

Form error (@633nm)

< 0.25 waves

Centration /parallelism

< 1 arc minute


< 40/20

Typical coatings

BBAR @ 1-7µm

DLC @ 1-7µm

Contact our multilingual technical sales team and discover how Knight Optical’s high quality Magnesium Fluoride optical components and service can improve your instrumentation and supply chain experience.

Uncoated, 1mm thick

Additional Information

  • Magnesium fluoride is the hardest of the fluoride materials used in optical components, and so is often used where durability is desired., especially when used in harsh conditions.
  • It can be cut in different orientations to produce either minimal or maximum birefringence, dependent on the application it is intended for.

Typical Applications

Rochon Polariser
  • Magnesium fluoride exhibits slight birefringence and therefore is often the substrate used in Rochon polarisers, which is made from two birefringent prisms. Other substrates such as calcite or crystalline quartz are also used.
Retarder plates
  • Due to magnesium fluorides birefringence it is also used as the substrate for retarder plates, such as quarter-wave plates.
Excimer Lasers
  • Magnesium fluoride transmits into the vacuum ultraviolet (VUV), it is durable and creates minimal aberrations. For excimer applications, magnesium fluoride would be cut in such a way to produce minimal birefringence. It is often the substrate used for excimer laser mirrors along with calcium fluoride.


Our 2022/2023 Catalogue

Inside Knight Optical’s catalogue you’ll find details of the industries we serve as well as the many other services we can offer. It also showcases hundreds of our most popular products, supported by useful technical information, to help you choose the right part for your application.
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