Germanium - Ge
lenses, windows, mirrors, filters and prisms
Click here to download PDF version of this page.Germanium has a high refractive index making it essential to add anti-reflection coatings to improve its transmission. It is inert, mechanically rugged and fairly hard making it suitable for external Infrared applications with durable AR coatings. Widely used in Infrared systems and as substrates for optical bandpass filters in the region from 2-14 microns. Available as generated lens blanks, polished windows, lenses and prisms with AR coatings, including Hard Carbon coating. The transmission of Germanium is very sensitive to temperature and above 70°C becomes opaque.
| Transmission Range | 1.8 - 23.0 µ |
| Crystal Structure | Diamond |
| Cleavage Plane | 111 |
| Colour | Metalic lustre |
| Density | 5.327 (25°) |
| Melting Point (°) | 942 |
| Reflection Loss | 52.9% (10µ) for 2 surfaces |
| Solubility index | Insoluble |
| Hardness (Knoop) | 692 |
| Thermal Conductivity (cal/cm sec°C) | 0.14 (20°C) |
| Thermal Expansion coefficient (/°C) | 5.5x10-6(25°C) |
Whilst every effort has been made to verify the data provided, no responsibility can be accepted for its accuracy