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RONAR-SMITH® LASER OPTICS & IR IMAGING

Infrared Optical Material - MgF2

Infrared Optical Material - MgF2 |CaF2|GaAs | Ge | ZnSe | ZnS |Sapphire| Si  |
Magnesium fluoride is transparent over an extremely wide range of wavelengths. The effective transmission range is 0.11 ¦Ìm - 7.5 ¦Ìm (ultraviolet to infrared). Irradiation does not lead to color centers. Magnesium fluoride is a rugged, hard material which is resistant to thermal and mechanical shock. Considerable mechanical shock is needed to cause cleavage which is near perfect when it occurs. The natural form of MgF2 is known as Sellaite. Magnesium fluoride is a positive birefringent crystal grown normally to 135 mm diameter by vacuum Stockbager technique, seeding along the C-axis. Thin layers of MgF2 are frequently applied to the surfaces of optical elements as part of optical coatings such as anti-reflective coatings.

Magnesium Fluoride (MgF2)

BASE PROPERTIES

PARAMETER

VALUE

OPTICAL  

Transmission Range

0.11 to 7.5 microns

Refractive Index

N0=1.3836 Ne=1.3957 at 0.405 microns

Reflection Loss

11.2% at 0.12 microns (2 surfaces)

Restrahlen Peak

20 microns

dN/dT

+2.3 and +1.7 x 10-6e/ ¡ãC at 0.4 microns

PHYSICAL  

Density

3.177 g/cm3

Melting Point

1255 ¡ãC

Thermal Conductivity

0.3 W/(m K) at 27 ¡ãC

Thermal Expansion

13.7and 8.48 x 10-6e/ ¡ãC

Hardness

Knoop 415 kg/mm2

Specific Heat Capacity, cal/(g K)
at 298 K
at 1700 K

0.24
0.362

Dielectric Constant

4.87 parallel and 5.45 perpendicular

Young's Modulus (E)

138.5 GPa

Shear Modulus (G)

54.66 GPa

Bulk Modulus (K)

101.32 GPa

Elastic Coefficients

C11=140.2 C12=89.5 C44=56.8
C33=204.7 C13=62.9 C66=95.7

Apparent Elastic Limit

49.64 MPa

Poisson Ratio

0.276

CHEMICAL

Solubility

<0.0002 g/100g water at 0 ¡ãC

Molecular Weight

62.32

Class/Structure

Tetragonal, can cleave on C-axis

REFRACTIVE INDEX  

Wavelength, ¦Ìm

0.20

0.23

0.27

0.34

0.56

Refractive Index (ne)

1.43

1.42

1.41

1.40

1.39

Refractive Index (no)

1.42

1.41

1.40

1.39

1.38

MgF2 Curve

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