Magnesium Fluoride is used for optical elements in both the
infrared and ultraviolet. Its useful transmission range is from
0.19µm; to 6.5µm. The refractive index varies from about 1.48 to
1.3. Magnesium Fluoride is a bi-refringence material and this
aspect should be taken into consideration before selection of this
material in an optical design. Janos uses only VUV grade material,
with the C-axis oriented to minimize birefringence. Irradiation
does not lead to color centers. This VUV material is the least
susceptible to radiation induced color centers.
Magnesium Fluoride is one of the lowest index infrared materials,
second only to Lithium Fluoride. It is resistant to thermal and
mechanical shock. The material is twice as hard as Calcium Fluoride
but only half as hard as Germanium. Magnesium Fluoride is
significantly more expensive than Calcium Fluoride and Barium
Fluoride, but usually not more expensive than Lithium Fluoride.
Magnesium Fluoride is similar to Calcium Fluoride in its resistance
0.121µm to 7.0µm
13.7 x 10-6 /°C Parallel to C-axis
8.48 x 10-6 /°C Perpendicular to C-axis
Polishes of 10-5, or 20-10 scratch-dig are achieved at extra costs
respectively mainly for UV applications. Typical specifications for
surface quality in the visible & near infrared regions are a
40-20 & 60-40 scratch dig in the 3 to 7µm range. MgF2 is
In the UV & Visible spectral regions, surface figure ranges
from 1/10 wave to 1/2 wave @ 0.6328µm. In the infrared, typical
required surface figure ranges from 1/2 wave to 2 waves @ 0.6328µm
& are specified depending on the system performance
AR Coating Options
Magnesium Fluoride can be AR coated for use in the infrared but
generally without much improvement in transmission due to its low
index of refraction & already high transmission.
Thermal imaging, Astronomical, Excimer laser applications.
Lenses, Aspheric lenses, Windows, Optical Beamsplitters, Optical
Filters, Wedges, Prisms.
Index of Refraction (n)