Germanium (Ge) possesses notable physical properties, characterized by its heavy and hard composition, boasting a Knoop Hardness of 780—nearly double that of MgF. With a density of 5.33 g/cm3, it becomes a favored choice for applications prioritizing durability. However, caution is advised for applications with routine temperatures exceeding 100°C, as Germanium’s transmission properties experience a sharp decline with increasing temperature, a phenomenon known as thermal runaway.

Despite its sensitivity to temperature, Germanium excels in IR laser applications, particularly in scenarios necessitating resilient optics. Additionally, it serves as an effective long pass filter, transmitting only wavelengths greater than 2 µm. Germanium is nonreactive to air, water, alkalis, and many acids, displaying high scratch resistance.

Avantier Germanium Windows are manufactured in sizes ranging from 2 to 100 mm, offering coatings in the 2-14µm or 8-12 µm range (BBAR coating or DLC/BBAR) upon request. Custom designs tailored to specific applications are also available in collaboration with our clients.

Our standard windows adhere to a flatness of ½ lambda, indicating minimal deviation from an ideal flat surface. Parallelism is maintained with a deviation of less than 3 arc minutes between optical surfaces, reducing image distortion and light degradation. The surface finish is set at 20-10, with no digs, and a transmission rate exceeding 47.5% at 3.7-4.8um, though adjustments can be made to meet custom specifications.

When it comes to cleaning Germanium Windows, precaution is essential due to the hazardous nature of Germanium dust. Handling with gloves is recommended, and hands should be washed after contact. Cleaning can be performed using reagent-grade acetone, ethanol, isopropyl alcohol, or methanol along with lint-free Germanium lens wipes. Nitric acid is an alternative option, but caution is required to prevent corrosion of neighboring optics or mounts.