Infrared Germanium Window

Germanium has a diamond-type structure, and N-type germanium single crystals are often used in infrared optics. Germanium material has a transparent area of 1.8 to 18um and is the most useful semiconductor substrate material for use as windows or lenses. It has high hardness as well as mechanical strength and is commonly used in the protective window of the front end of infrared imaging systems. Its geometry can be round, rectangular, octagonal, polygonal and other special types. To better understand the infrared germanium window, we will cover the following topics:

• Features of infrared germanium windows
• Typical applications for infrared germanium windows
• Material properties of N-type germanium single crystal
• The process of making an infrared germanium window

What are the properties of an infrared germanium window?

1. The transmittance of substrates in the 8 to 12um band range is about 47%. The double-sided high-efficiency anti-reflective film can effectively reduce the reflectivity, and the final average transmittance can reach more than 95%.
2. Can be cut into a variety of geometries to meet demanding installation requirements.
3. Excellent surface accuracy before and after coating ensure the imaging quality of the system.
4. Customized optical coatings are available for different applications.

What are the applications of infrared germanium window?

Infrared germanium window is widely used in 7.5~14um atmospheric window. Mature in low-speed aircraft and helicopter applications. Infrared night vision UAV, infrared night vision monitors and other aspects are also widely used. In addition, infrared germanium windows also have many applications in mid-wave infrared, such as infrared temperature measurement systems.

What substrate material is suitable for a typical infrared germanium window?

Germanium is chemically stable and opaque in the visible region. Germanium single crystal is the basic material for the preparation of infrared windows. Germanium crystals have the same atomic arrangement as diamond, with a face-centered cubic cell structure, with each unit cell containing 4 metal atoms. In single crystal germanium, n-type germanium single crystal has good infrared transmittance because the absorption section of electrons to photons is 1/20 of the absorption section of holes to photons. Therefore, most of the ones used in infrared optics are N-type germanium single crystals.


Due to the high refractive index of germanium single crystal (nd=4.0) and the reflection loss of the surface reaches about 53%, it is often necessary to coat its surface with a high-strength infrared anti-reflection protective film. On the one hand, the coating can reduce the surface reflection loss and improve the transmittance of the germanium window. On the other hand, it also plays a role in protecting the germanium window and improving the material's ability to resist rain and sand erosion. After the infrared germanium window is coated, the transmittance increases significantly, and the maximum transmittance can reach more than 98%.

How to produce an infrared germanium window?

Creator Optics uses high-quality infrared N-type single crystal germanium as the window substrate. These preferred germanium ingots are processed into the required exact geometric dimensions window blanks by equipment such as CNC cutting machines, cylindrical mills, multi-wire cutting machines, etc. These blanks will be subjected to multi-step CMP to meet the precision polishing requirements of infrared germanium windows. In general, these infrared germanium windows can also be designed and coated with optical films according to different application requirements. A typical example is the diamond-like film, which increases the transmittance of the infrared band while increasing the excellent hardness to cope with the erosion and damage of the germanium window surface in the harsh outdoor environment.

At present, the infrared germanium windows provided by Creator Optics are mainly as follows:

Conventional Infrared Germanium Windows

AR/DLC Coted Infrared Germanium Windows

How to guarantee the performance of infrared germanium windows?

All infrared germanium windows with or without IR optical coating supplied by Creator Optics are rigorously inspected. Qualified germanium ingot suppliers provide high quality and reliable window substrate materials. A full range of measuring instruments and equipment for geometry measurement, surface quality measurement, surface finish measurement, spectral characteristics measurement and environmental testing. Any infrared germanium window that meets the delivery conditions has factory quality certification.

    Standard Infrared Germanium windows >>>

    Detailed characteristics of germanium monocrystal >>>

* Want to know more about infrared germanium windows? Have a special question or application requirement about infrared germanium windows? Please contact our sales engineers directly.