| Materials | Optical grade germanium single crystals | Diameter Range | ~280mm |
| Thickness Tolerance | ±0.2mm (Optional: ±0.1mm or ±0.05mm) |
Surface Quality | 60/40 S/D |
| Frings (N) | customized | Irregularity (delta N) | customized |
| Chamfer | 0.1~0.3mmx45degree | Coating(optional) | AR/AR@7-14μm DLC/AR@7-14μm BBAR/BBAR@3-12μm See the curves below |
Physical and Optical Properties:
| Transmission Range | 1.8 to 23μm (1) | Refractive Index | 4.0026 at 11μm (1)(2) |
| Reflection Loss | 53% at 11μm (2 surfaces) | Absorption Coefficient | <0.027 cm-1 @ 10.6μm |
| Reststrahlen Peak | n/a | dn/dT | 396 x 10-6 /°C (2)(6) |
| dn/dμ = 0 | Almost constant | Density | 5.33 g/cc |
| Melting Point | 936 °C (3) | Thermal Conductivity | 58.61 W m-1 K-1 at 293K (6) |
| Thermal Expansion | 6.1 x 10-6 /°C at 298K (3)(4)(6) | Hardness | Knoop 780 |
| Specific Heat Capacity | 310 J Kg-1 K-1 (3) | Dielectric Constant | 16.6 at 9.37 GHz at 300K |
| Youngs Modulus (E) | 102.7 GPa (4) (5) | Shear Modulus (G) | 67 GPa (4) (5) |
| Bulk Modulus (K) | 77.2 GPa (4) | Elastic Coefficients | C11=129; C12=48.3; C44=67.1 (5) |
| Apparent Elastic Limit | 89.6 MPa (13000 psi) | Poisson Ratio | 0.28 (4) (5) |
| Solubility | Insoluble in water | Molecular Weight | 72.59 |
| Class/Structure | Cubic Diamond, Fd3m |
Germanium domes is a special type of windows which is ideal for IR applications(especially for defense and aerospace application) with its broad transmission range and opacity in the visible portion of the spectrum. Germanium domes is commonly used in IR thermal imaging cameras typically operating in the 2 µm to 14 µm spectral range, covers the LWIR (8-12μm) and MWIR (3-5μm) thermal imaging wavelength range. Germanium windows can be AR coated with Diamond (DLC coating or Hard carbon coating) producing an extremely tough front optic.
Technical Images:
1. Transmission curve for Ge windows with coating AR/AR of 1mm thickness
