13 October 2010 Development of immersed diffraction grating for the TROPOMI-SWIR spectrometer
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We have developed a novel diffraction grating based on lithographical techniques and anisotropic etching in silicon. The grating is designed for the short-wave-infrared channel of the TROPOMI imaging spectrometer that will be launched on ESA's Sentinel 5 Precursor mission to monitor trace gases in the earth atmosphere. Stringent requirements on both the imaging properties and the quality of the spectra translate to a high-tech grating. In our design the dispersion and resolution is increased with a factor 3.4 with respect to conventional gratings by using the grating in immersion, such that diffraction takes place inside the silicon grating material. By lithographic patterning and anisotropic etching of the mono-crystalline silicon we precisely control line spacing and blaze angle. The grating has a line spacing of 2.5 μm and is operated in sixth order. We show that an efficiency of 60% is reached on a 50 x 60 mm2 grating surface. We compare our test results with numerical calculations for grating efficiency for both polarizations and find good agreement.
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A. H. van Amerongen, A. H. van Amerongen, H. Visser, H. Visser, R. J. P. Vink, R. J. P. Vink, T. Coppens, T. Coppens, R. W. M. Hoogeveen, R. W. M. Hoogeveen, } "Development of immersed diffraction grating for the TROPOMI-SWIR spectrometer", Proc. SPIE 7826, Sensors, Systems, and Next-Generation Satellites XIV, 78261D (13 October 2010); doi: 10.1117/12.869018; https://doi.org/10.1117/12.869018

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