Wuhan Siwer Optics Co.,Ltd
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The transmittance range of the optical germanium material is 2-14 um, and the refractive index is as high as 4. Germanium lens and germanium window are widely used in thermal imaging system.
Germanium window is a common protective window in infrared imaging system. Its material quality, surface smoothness, parallelism, surface quality and coating quality will directly affect the imaging effect.
The resistivity of optical grade single crystal germanium material we choose is usually 5-40 Ohms. If the customer requests, we can also choose germanium material with specified resistivity.
Due to the high refractive index and high surface reflectivity of germanium (r > 30%), optical germanium windows usually need AR coating on its surface.
If the equipment is used in a bad environment, the outer side of the germanium protection window needs to be coated with DLC Coating.DLC Coating has excellent wear resistance, acid resistance and corrosion resistance.
| Material | Single Crystal Germanium |
| AR Coating Range | 3-5um,8-12um,3-11um |
| Reflectance over AR Coating Range @ 0° AOI | Ravg < 2%,3-5um or 8-12um Ravg<5%,3-11um |
| Transmission over AR Coating Range @ 0° AOI | Tavg > 94%,3-5um or 8-12um |
| Diameter Tolerance | +0.0/-0.1 mm |
| Thickness Tolerance | ±0.1 mm |
| Parallelism | 3 arc min |
| Surface Quality | 60-40 Scratch-Dig |
| Surface Flatness (Plano Side) | λ/2 at 633nm |
| Surface Irregularity (Peak to Valley) | λ/2 at 633nm |
| Clear Aperture | >Ø10.16 mm (Ø1/2" Lenses) >Ø20.32 mm (Ø1" Lenses) |
| Design Wavelength | 10.6 μm |
| Chemical Formula | Ge |
| Crystal Form | Poly or Single Crystal |
| Crystal Class | Cubic |
| Resistivity, Ohm*cm | 0.01-40 |
| Lattice Constant, Å | 5.66 |
| Molecular Weight | 72.6 |
| Density, g/cm3 at 300 K | 5.33 |
| Dielectric Constant for 9.37 x 109 Hz at 300 K | 16.6 |
| Melting Temperature, K | 1210 |
| Thermal Conductivity, W/(m K) at 293 K | 59 |
| Thermal Expansion, 1/K at 298 K | 6.1 x 10-6 |
| Specific Heat, cal/(g K) at 273-373 K | 0.074 |
| Debye Temperature, K | 370 |
| Bandgap, eV | 0.67 |
| Solubility in water | None |
| Knoop Hardness, kg/mm2 | 800 |
| Mohs Hardness | 6.3 |
| Young's Modulus, GPa | 102.66 |
| Shear Modulus, GPa | 67.04 |
| Bulk Modulus, GPa | 77.86 |
| Poisson's Ratio | 0.278 |
Production process