Germanium (Ge) Domes
Maximum Diameter: Up to 280mm, allowing for large-scale optical applications without compromising performance.
Wide Operation Wavelength Range: Germanium domes exhibit broad transmission capabilities across the infrared spectrum, from 2µm to 14µm. This makes them ideal for capturing both mid-wave infrared (MWIR) and long-wave infrared (LWIR) wavelengths, crucial for thermal imaging and sensing applications.
Mechanical Ruggedness: Known for their durability and mechanical strength, germanium domes withstand harsh environments encountered in aerospace and defense operations. They provide a reliable protective barrier for sensitive optical components.
Low Chromatic Dispersion: Maintaining minimal chromatic dispersion ensures that germanium domes deliver high-resolution images with accurate color representation in the infrared spectrum.
Germanium domes are specialized optical windows crafted from single-crystal germanium. They feature a curved profile and are highly prized for their exceptional performance in infrared (IR) applications. With a transmission range spanning from 2µm to 14µm, these domes effectively block visible light while allowing IR radiation to pass through unhindered. They exhibit minimal chromatic dispersion, ensuring clear and accurate imaging in IR spectrums. Beyond optical excellence, Germanium domes serve as robust protective barriers, safeguarding sensitive components from harsh environmental conditions. They are widely utilized in IR thermal imaging cameras, IR sensors, and various other IR optical systems across different industries.
Material and Optical Properties:
- Germanium is chosen for its optical transparency in the infrared spectrum, typically ranging from 2µm to 14µm. This makes it suitable for IR thermal imaging applications.
- It effectively blocks visible light, which is crucial for IR cameras to operate without interference.
- Germanium has low chromatic dispersion, meaning it does not separate different wavelengths of light (colors) much, ensuring better focus in IR imaging.
Applications:
- Germanium domes are used extensively in IR thermal imaging cameras that operate in the long-wave infrared (LWIR, 8-12µm) and mid-wave infrared (MWIR, 3-5µm) spectral regions.
- Germanium domes serve as protective barriers, shielding sensitive IR components from harsh environments while allowing the passage of IR radiation.
Durability and Coatings:
- Germanium is rugged and can withstand extreme environments, making it ideal for aerospace and defense applications where reliability is critical.
- Germanium domes can be coated with materials like Diamond-Like Carbon (DLC) or hard carbon coatings to enhance their durability and scratch resistance, ensuring long-term performance in challenging conditions.
Manufacturing and Design:
- Germanium domes are typically manufactured from single-crystal germanium, ensuring high optical quality.
- Their curved profile is designed to minimize optical aberrations and maximize transmission efficiency in the IR spectrum.
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) |
| Hardness | Knoop 780 |
| Thermal Expansion | 6.1 x 10-6 /°C at 298K (3)(4)(6) |
| Thermal Conductivity | 58.61 W m-1 K-1 at 293K (6) |
| 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) |
| Elastic Coefficients | C11=129; C12=48.3; C44=67.1 (5) |
| Bulk Modulus (K) | 77.2 GPa (4) |
| Shear Modulus (G) | 67 GPa (4)(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 |
