Near infrared cryogenic tunable solid Fabry-Perot spectrometer

We have developed a high resolution near-infrared temperature tunable cryogenic spectrometer with solid Fabry-Perot etalons. It is designed and built for diffuse emission of ionized hydrogen Brγ studies, although with the appropriate pre-filter it can be configured for any near infrared lines. The etalons made from silicon and germanium operate near 77K. The high refractive index of these etalons allows for the construction of a very compact spectrometer. Germanium etalon with 20mm clear aperture is equivalent to a gas spaced Fabry-Perot interferometer of about 80 mm in diameter. A strong temperature dependence of the refractive index for these two materials makes it easy to tune etalons. Combination of these factors allowed to build a compact, high resolution (R=12000) high throughput instrument.