Material
Usable
Transmission
Range (μm)
Index of
Refraction
Abbe
Number
Density
(g/cm3)
CTE
(x 10-6/°C)
dn/dT
(x 10-6/°C)
Knoop
Hardness
(kg/mm2)
Properties Typical Applications
Calcium Fluoride
(CaF) 0,25 - 7,0 1,434 95,1 3,18 18,85 -10,6 158,3 Low absorption; high refractive index
homogeneity
2Spectroscopy, Semiconductor Processing,
Cooled Thermal Imaging
Chalcogenide Glass
(IG6) 0,9 - 13,0 2,795 N/A 4,63 20,7 35,5 1,04 Low thermal change in refractive index and
dispersion; excellent moldability
Thermal Imaging, Color Correction in the
2 - 12 μm Spectrum
Germanium
(Ge) 2,0 - 14,0 4,003 N/A 5,33 6,1 396 780 High index of refraction; high Knoop hardness;
excellent MWIR to LWIR Transmission Thermal Imaging, Rugged IR Imaging
Magnesium Fluoride
High CTE; low index of refraction; good
(MgF) 0,12 - 7,0 1,413 106,2 3,18 13,7 1,7 415 transmission from visible to MWIR
2Broadband Applications not requiring
Anti-Reflection Coatings
Barium Fluoride
(BaF2) 0,2 - 12,0 1,475 81,78 4,89 18,1 15,2 82 Broad transmission range; resistant to high
energy radiation FTIR Spectroscopy, Scintillation
Potassium Bromide
(KBr) 0,25 - 26,0 1,527 33,6 2,75 43 -40,8 7 Good resistance to mechanical shock; water
soluble; broad transmission range FTIR Spectroscopy
Sapphire
(Al0) 0,2 - 5,5 1,768 72,2 3,97 5,3 13,1 2200 Excellent durabilty; good MWIR transmission IR Laser Systems, Spectroscopy, and
Rugged Environmental Equipment
23Silicon
(Si) 1,2 - 7,0 3,422 N/A 2,33 2,55 1,6 1150 Low cost; lightweight Spectroscopy, MWIR Laser Systems,
THz Imaging
Sodium Chloride
(NaCl) 0,25 - 16,0 1,491 42,9 2,17 44 -40,8 18,2 Low cost; water soluble; excellent broadband
transmission; sensitive to thermal shock FTIR Spectroscopy
Zinc Selenide
(ZnSe) 0,6 - 18,0 2,403 N/A 5,27 7,1 61 120 Low absorption; high resistance to
thermal shock CO2 Laser Systems and Thermal Imaging
Zinc Sulfide
(ZnS) 0,4 - 12,0 2,631 N/A 5,27 7,6 38,7 120 Excellent transmission from visible to LWIR;
harder and more chemically resistant than ZnSe Thermal Imaging
122 +44 (0) 1904 788600 | Edmund Optics® N NEW PRODUCT NEW LOW PRICE
testing & detection targets illumination cameras imaging lenses microscopy lasers optomechanics optics
Substrate: Germanium (Ge)
Dimensional Tolerance (mm): +0,0/-0,1
Thickness Tolerance (mm): ±0,1
Surface Flatness (@ 10,6 μm): l/10
Surface Quality: 60-40
Parallelism (arcmin): ≤ 1
Knoop Hardness (kg/mm2): 780
Clear Aperture (%): 90
AR Coating:
Ravg @ 8 - 12 μm: ≤ 0,5%
Adhesion: per MIL-C-48497A Paragraph 4.5.3.1
Abrasion: Moderate, per MIL-C-48497A Paragraph 4.5.3.3
Humidity: per MIL-C-48497A Paragraph 4.5.3.2
Temp. (°C): -80 to +160 per MIL-C-48497A Paragraph 4.5.4.1
Solubility and Cleaning: per MIL-C-48497A Paragraph 4.5.4.2
DLC Coating:
Adhesion: per MIL-M-13508C Paragraph 4.4.6
Abrasion: Severe, per MIL-C-675C Paragraph 4.5.10
Humidity: ≥ 24 Hours per MIL-C-675C paragraph 4.5.8
Salt Solubility: ≥ 24 Hours Immersion per MIL-C-675C paragraph
4.5.7
Salt Spray: ≥ 24 Hours per MIL-C-675C paragraph 4.5.9
Temp. (°C): -80 to +160 per MIL-M-13508C Paragraph 4.4.4
Wiper: ≥ 5,000 Wipes of Sand/Slurry per TS-1888
TECHNICAL NOTE
IR Selection Guide
Infrared (IR) radiation is characterized by wavelengths ranging from 0,750 -1.000 μm (750 - 1.000.000 nm), and has important applications in defense, imaging,
spectroscopy, and the life sciences. While dozens of IR transmitting materials exist, a select few are predominantly used within the optics, imaging, and
photonics industries to manufacture off-the-shelf components. Each have their own unique optical, mechanical, and thermal attributes that distinguish them
from each other, in addition to making them suitable for specific applications. The following tables provide a comparison of some commonly used substrates.
When choosing the correct IR material, there are a few common considerations:
1. Thermal Properties – Frequently, optical materials are placed in environments where they are subjected to varying temperatures. Additionally, a common
concern with IR applications is their tendency to produce a large amount of heat. A material’s thermo-optic coefficient (dn/dt) and coefficient of thermal
expansion (CTE) should be evaluated to ensure the optic is suitable for the intended environment.
2. Optical Properties – Different applications operate within different regions of the IR spectrum, so transmission within the application range needs to be
considered. Likewise, materials with low dispersion should be considered for broadband applications, while high dispersion materials are suited for monochromatic
applications. Materials with a high index of refraction often require anti-reflection coatings for suitable transmission.
3. Mechanical Properties – Infrared optical materials can vary from heavy and rugged, to light and brittle. A low Knoop Hardness indicates a soft material.
Diamond-Like Carbon (DLC) Coated Germanium Windows
• Meets Severe Abrasion Requirements of
MIL-C-675C
• ≥ 90% Transmission from 8 - 11,5 μm
• Ideal for Harsh Environments
TECHSPEC® Diamond-Like Carbon (DLC) Coated
Germanium Windows have been designed with durability
in mind. Featuring a high efficiency broadband
anti-reflection coating on one surface, and a
specially designed DLC coating on the other surface,
these windows feature excellent transmission and
environmental resistance. The DLC coated surface
is designed to withstand temperature cycling from
-80 to +120°C, salt spray for a continuous period of
24 hours, salt solubility for an immersion period of
24 hours, and 5.000 wiper oscillations in a sand and
slurry mixture. Further, TECHSPEC® DLC Coated
Germanium Windows meet the MIL-C-675C requirements
for severe abrasion.
TECHSPEC® Diamond-Like Carbon (DLC) Coated Germanium Windows
Diameter (mm) Thickness (mm) Stock No. Price
25,0 1,0 #13-795 €370,00
25,0 3,0 #13-796 €370,00
50,0 1,0 #13-797 €735,00
50,0 3,0 #13-798 €735,00
75,0 5,0 #13-799 €1.285,00
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