Germanium etalons  have a high index (~4.0 depending on wavelength) that creates a reasonably high finesse without any coatings.  They also remain transmissive farther out into the infrared than silicon etalons, the germanium etalon will still provide a decent signal at a wavelength of 14um. The high temperature sensitivity of germanium is similar to silicon and can also be useful (or problematic).  These etalons are often used to monitor the wavelengths of tunable lasers (like lead salt or quantum cascade lasers) in the mid-infra red in applications such as Tunable Diode Laser Absorption Spectroscopy, TDLAS.   A portion of the output from a tunable laser is directed at the germanium etalon. As the laser is tuned, the transmission through the etalon is modulated with a spacing between transmission peaks equal to the etalon FSR.

• Material: Germanium
• Wavelength range: IR 2.5um to 14um
• Wedge < 5.0 arc second*
• Clear aperture: 80% diameter
• Surface quality: 80/50 or better
• Surface figure: λ/10
• Diameter: 25.4
• Finesse and FSR are dependent on the wavelength
• * If your etalons require coatings then we can use our fluid jet polishing system to reduce the wedge and increase the finesse

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Learn More about etalons!

Etalons

Learn more about the various types of etalons we can make (and see some cool pictures)

Optical Design Center

Design etalons, lenses, resonators, VIPA's and explore optical material properties.

Fluid Jet Polishing

Learn more about Fluid Jet Polishing, it is one of our enabling technologies