Germanium(Ge) Double-Concave Lenses
Germanium (Ge) single crystal is a chemically inert material with a transmission spectral range of 2-12 μm. It is a very commonly used infrared optical material with high hardness, good thermal conductivity, and insoluble in water. Widely used in infrared imaging systems and infrared spectrometer systems. Germanium single crystal has good mechanical properties and thermal conductivity, and the absorption at 10.6μm is very small. It is an ideal material for CO2 laser lenses, windows and output coupling mirrors. Germanium single crystals are also used as substrate materials for various infrared filters
Germanium(Ge) double concave lens is similar to a plano-concave lens in that the focal length is negative, but the light incident in parallel diverges outward. It’s been widely applied for laser systems and infrared systems,such as optical instruments,laser device,optical fiber communication ,optical measurement and inspection ect.
Our Company can provide Germanium(Ge) double concave lens with diameters from 2-300mm and thicknesses from 0.12-60mm (accuracy up to 20-10, 1/10L@633nm),coating AR, BBAR, AF or upon request.
Technical parameters of Germanium(Ge) Double-Concave Lens
Diameter | 2-300mm |
Focal length | 15-5000mm |
Thicknesses | 0.12-60mm |
Dimension tolerance | +0/-0.1mm |
Thickness tolerance | ±0.1mm |
Surface quality (scratch & dig) | 60-40, 40-20, or better |
Surface accuracy | λ/2, λ/4 or better |
Parallelism | 3' ,30'' |
Bevel | 0.1~0.3mm x 45 degree |
Clear aperture | >85%,>90% |
Coating | AR coating or cutom |
Material properties of Germanium(Ge)
| Optical Properties | |
| Transmission Range | 2-15μm |
| Reflection Loss | 4.0028@10.6μm |
| Absorption Coefficienet | 1.3×10-3@3.8μm |
| 3×10-2@10.6μm | |
| Structure | Cubic Crystal System |
| Cleavage Planes | <111> |
| Physical Properties | |
| Density[g/cm3] | 5.33 |
| Melting Point [℃] | 936 |
| ThermalConductivity [W/(m×K)] | 58.61 @ 293K |
| Thermal Expansion [10-6/K] | 6.1 @ 298K |
| Knoop Hardness [kg/mm2] | 780 |
| Specific Heat Capacity [J/(kg×K)] | 310 |
| Dielectric Constant | 16.6 @9.37 GHz |
| Young's Modulus (E) [GPa] | 102.7 |
| Shear Modulus(G) [GPa] | 67 |
| Bulk modulus(K) [GPa] | 77.2 |
| Poisson Coefficient | 0.28 |
| Chemical Properties | |
| Solubility / g/L | Inoluble |
| Molecular Weight / g/mol | 72.61 |
Transmission curve
Germanium is widely used because of its high refractive index, large transmission distance range and robust mechanical properties. Optical grade germanium crystal has a wide infrared transmission band (available in both 3~5μm and 8~12μm bands) and is a good material for making infrared optical lenses, mostly used in thermal imaging cameras and infrared lasers.
