The Germanium as a mono crystal primarily used in semi-conductor is non-absorptive at 2μm to 20μm IR regions. It is used here as an optical component for IR region applications.
◦These germanium windows do not transmit at 1.5µm region or below, therefore its main application is in the IR regions.
◦Germanium windows can be used in various infrared experiments.
Attention
▶Germanium windows have a shiny metal surface; it reflects and absorbs but does not transmit in the visible regions.
▶Germanium windows surface reflection results in transmittance loss of 42%. (Measured data 1 surface reflection at 35%)