Optical Windows
Optical windows are transparent components made of materials like glass or crystal that are used to protect and control the flow of light in optical systems. IR windows and optics for use in FTIR Spectroscopy and CO2 lasers. This includes discs, rectangular plates and various other geometries.
In various fields, optical windows serve many purposes. They act as protective barriers, shielding sensitive optical components from environmental factors such as dust, moisture, and contaminants. Additionally, they enable the transmission of light while minimizing distortion, reflection, and absorption, thus maintaining the integrity of the optical system.
Optical windows are employed in a wide range of applications, including scientific research, industrial manufacturing, aerospace, defense, and telecommunications. They are utilized in optical instruments like cameras, microscopes, telescopes, lasers, and sensors. By providing a stable optical interface, optical windows facilitate accurate measurements, imaging, and analysis of light, enabling advancements in numerous fields.
Optical windows come in many shapes and sizes but a major factor is their material. The types of materials that an optical window is constructed from dictate the wavelengths (measured in nm) that they can view. In IR It is extremely important that selecting the right material is done to avoid many a headache and a waste of money and time.
If you are having choice fatigue and are getting overwhelmed by all the options please check out our optical window guide.
Germanium (Ge) Windows
Germanium (Ge) Windows
Germanium or Ge has high transmission in the range of 2-16μm and is best used in mid-IR and long wave IR applications. Due to its low dispersion, it is a common choice for use in low power CO2 laser applications. Germanium also is opaque throughout the entire visible spectrum, making it ideal for applications where only IR transmission is desired.
Germanium is inert to air, water, alkalis and many acids, which makes it a robust, versatile material.
Firebird provides these in several uncoated stock configurations in circular and rectangular shapes but can provide them customized and coated to your specifications.
Germanium (Ge) Specs:
Transmission of uncoated Germanium window:
Transmission of BBAR-coated Germanium window (3-12 microns):
General specs:
| Wavelength range: 2-16µm | Coating: Uncoated |
|---|---|
| Diameter tolerance: ±0.2mm | Surface Quality: 60/40 |
| Thickness tolerance: ±0.1mm | Paralellism: <1 arc minute |
| Clear Aperture: 90% | Density: 5.33g/cm3 | Melting point: 938.2ºC | Young's Modulus: (GPa): 102.7 | Coefficient of Thermal Expansion: 5.9 x 10-6/°C | Knoop Hardness: 780kg/mm2 |
Expanded Germanium Properties:
| Chemical formula | Ge |
|---|---|
| Crystal form | Monocrystal, orientation <111>, N-type |
| Crystal Class | Cubic |
| Resistivity, Ohm*cm | 5-40 | Lattice Constant, Å | 5.66 | Molecular Weight | 72.60 | Density, g/cm3 at 300 K | 5.33 | Dielectric Constant for 9.37 x 109 Hz at 300 K | 16.6 | Melting Temperature, K | 1210 | Thermal Conductivity, W/(m K) at 293 K | 59 | Thermal Expansion, 1/K at 298 K | 6.1 x 10-6 | Specific Heat, cal/(g K) at 273-373 K | 0.074 | Thermal Expansion, 1/K at 298 K | 6.1 x 10-6 | Debye Temperature, K | 370 | Bandgap, eV | 0.67 | Solubility in water | None | Knoop Hardness, kg/mm2 | 800 | Mohs Hardness | 6.3 | Young's Modulus, GPa | 102.66 | Shear Modulus, GPa | 67.04 | Bulk Modulus, GPa | 77.86 | Poisson's Ratio | 0.278 |
Refractive Index of Germanium:
| µm | No |
|---|---|
| 2.058 | 4.102 |
| 2.153 | 4.0919 |
| 2.313 | 4.0786 | 2.437 | 4.0708 | 2.577 | 4.0609 | 2.714 | 4.0562 | 2.998 | 4.0452 | 3.303 | 4.0369 | 4.258 | 4.0216 | 4.866 | 4.017 | 6.238 | 4.0094 | 8.660 | 4.0043 | 9.720 | 4.0034 | 11.04 | 4.0026 | 12.00 | 4.0023 | 13.02 | 4.0021 |
Further Reading:
Finding the right optical window can be an exercise in choice fatigue. Let us help!