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Germanium Wedged Windows![]()
Back Reflections from Wedges Are not Collinear with the Incident Beam WW91050 Ø1" WW90530-E3 Ø1/2" ![]() Please Wait
Features
Thorlabs offers Ø1/2" and Ø1" wedged germanium (Ge) windows that are uncoated or AR-coated for 7 - 12 µm. These wedged optics eliminate fringe patterns and can be used to help avoid cavity feedback. Windows are useful for protecting a laser output from environmental effects and for beam sampling applications. Due to its broad transmission range (2.0 - 16 µm) and opacity in the visible portion of the spectrum, germanium is well suited for IR laser applications. As shown in the Graphs tab, this substrate also acts as a longpass filter for wavelengths greater than 2 µm. In addition, germanium is inert to air, water, alkalis, and acids (except nitric acid). Germanium's transmission properties are highly temperature sensitive; in fact, the absorption becomes so large the material is nearly opaque at 100 °C and completely non-transmissive at 200 °C. When handling optics, one should always wear gloves. This is especially true when working with germanium, as dust from the material is hazardous. For your safety, please follow all proper precautions, including wearing gloves when handling this material and thoroughly washing your hands afterward. In addition to the germanium wedged windows offered here, Thorlabs also offers wedged windows with other substrate materials (see the selection guide above and to the right). Wedged Laser Windows with AR coatings centered around common lasing wavelengths and wedged Beam Samplers with broadband AR coatings on only one face are also available. Additionally, wedged windows with our standard AR coatings or custom sizes and thicknesses are available; please contact Tech Support for more information. We also supply planar windows with a variety of substrate materials and coating options. We also supply planar windows with a variety of substrate materials and coating options. All of these germanium wedged windows can be ordered uncoated or with a 7 - 12 µm AR coating (designated as -E3). Thorlabs' high-performance -E3 broadband AR coating has an average reflectance of less than 1.0% (per surface) across its specified wavelength range (denoted by the shaded blue area in the Coating graph below). The AR coating provides good performance for angles of incidence (AOI) between 0° and 30° (0.5 NA). The substrate transmission graph below shows the transmission of light through an uncoated Ge substrate. Please contact Tech Support to order optics with custom coatings or sizes. Uncoated Ge Window![]() Click to Enlarge Click for Raw Data This graph shows the full scale measured transmission of an uncoated germanium window at normal incidence. ![]() Click to Enlarge Click for Raw Data This graph shows the measured transmission of an uncoated germanium window at normal incidence in the visible wavelength range. The values reported in the visible and near infrared are limited by the noise floor of the spectrometer used. Please note that out-of-band transmission is not monitored during production and will vary from lot to lot. Ge Window, AR Coated for 7 - 12 µm![]() Click to Enlarge Click for Raw Data This plot gives the measured reflectance (per surface) at normal incidence of our AR-coated germanium window. The average reflectance is <1.0% per surface within the shaded wavelength range of 7 µm - 12 µm. ![]() Click to Enlarge Click for Raw Data Shown above is a graph of the measured transmission of a 5 mm thick AR-coated germanium substrate. The blue shaded region denotes the 7 - 12 μm spectral range where we suggest using these Ge wedged windows. For this wavelength range, the measured transmission is in excess of 90%.
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