Germanium

Germanium is a critical material in the field of optics and photonics, prized for its unique optical properties and wide-ranging applications.

One of its primary attributes is its excellent transparency in the infrared spectrum, particularly in the mid-infrared (mid-IR) and far-infrared (far-IR) regions. Germanium's transparency extends from approximately 2 to 16 microns, making it exceptionally well-suited for infrared optics.

Germanium possesses a relatively high index of refraction, typically around 4 in the mid-IR range, which makes it an essential material for the design and fabrication of optical components such as lenses, windows, prisms, and mirrors. These components are crucial for various applications in infrared spectroscopy, thermal imaging, night vision systems, and laser systems.

Manufacturing processes for optical Germanium involve precision techniques such as single-crystal growth and diamond turning to achieve the required optical quality and surface finish.

In addition to its optical transparency and refractive properties, Germanium exhibits excellent thermal conductivity, which allows it to dissipate heat effectively. This thermal conductivity is advantageous for applications where temperature management is critical, such as in thermal imaging systems and infrared detectors.

Germanium is also widely used in semiconductor devices, including infrared detectors and photodetectors, due to its unique electronic properties, such as its narrow bandgap.

Despite its advantages, Germanium is more expensive and less abundant than some other optical materials, which can impact its widespread adoption in certain applications. However, its exceptional optical performance and compatibility with infrared wavelengths make it indispensable for a variety of advanced optical systems and devices.

Optical Grade Germanium (Ge) is a high-index material used in infrared optics with the following technical properties:

Transmission Range: 1.8 to 23 μm

Refractive Index: 4.0026 at 11 μm

Reflection Loss: 53% at 11 μm (2 surfaces)

Absorption Coefficient: <0.027 cm-1 @ 10.6 μm (typical)

Reststrahlen Peak: n/a

dn/dT: +396 x 10-6 K-1

Density: 5.33 g/cc

Melting Point: 937.4°C

Thermal Conductivity: 58.62 W m-1 K-1 @ 293 K

Thermal Expansion: 6.1 x 10-6/°C @ 298 K

Hardness Knoop: 780

Specific Heat Capacity: 310 J Kg-1 K-1

Dielectric Constant: 16.6 at 9.37 GHz at 300K

Young’s Modulus (E): 102.7 GPa

Shear Modulus (G): 67 GPa

Bulk Modulus (K): 77.2 GPa

Elastic Coefficients: C11 = 129, C12 = 48.3, C44 = 67.1

Apparent Elastic Limit: 89.6 MPa (13000psi)

Poisson Ratio: 0.28

Solubility: Insoluble in water

Molecular Weight: 72.59

Class/Structure: Cubic Diamond, Fd3m

Please note that these values are typical and may vary based on the grade and manufacturing process of the material