The germanium material has a high refractive index (approximately 4.0 in the 2-14μm band). When used as windows, it can be coated as needed to improve the transmittance of the corresponding band. Moreover, the transmission properties of germanium are extremely sensitive to temperature changes (the transmittance decreases with increasing temperature), therefore, they can only be used below 100°C. The density of germanium (5.33 g/cm3) should be considered in the design of a system with strict weight requirements. The germanium window has a wide transmission range (2-16μm) and is opaque in the visible spectrum, which is particularly suitable for infrared laser applications. The Knoop hardness of germanium is 780, which is about twice the hardness of magnesium fluoride, which makes it more suitable for applications in the IR field of variable optics.
Material: Ge Dimension Tolerance: 0.0/-0.1mm Thickness Tolerance: ±0.2mm Clear Aperture: ≥90% Surface Quality: 40/20 Flatness: λ/4@633nm Parallelism: ≤3’ Chamfer: 0.3×45° AR coating: Ravg<5% per surface@8-12μm Other coating is customized.