27 June 2006 Performance of large chemically etched silicon grisms for infrared spectroscopy
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Abstract
FORCAST is a mid/far-IR camera for use on NASA's SOFIA airborne observatory. We are fabricating monolithic silicon grisms to retrofit a spectroscopic capability for this facility-class instrument without affecting the imaging optics. The grisms will operate in the 5-8, 17-28, and 28-37 μm wavelength ranges. We will cover the 5-8 μm range in one exposure at a resolving power R=1200 with a 2 arcsecond slit using two grisms with one serving as a cross-disperser. For the 17-28 and 28-37 μm ranges, the resolving powers are R~140, 250 when used in low order with a slit of 3 arcseconds. We illustrate aspects of fabrication and testing during the grism development, and summarize the performance of the gratings at near- and mid-IR wavelengths. These gratings rely on procedures that can be used for modest sized (~10 cm) silicon pieces, thereby providing dispersive elements with good optical performance and large slit width-resolving power products from 1.2-8.1 μm and beyond 17 μm.
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D. J. Mar, J. P. Marsh, D. T. Jaffe, L. D. Keller, K. A. Ennico, "Performance of large chemically etched silicon grisms for infrared spectroscopy", Proc. SPIE 6269, Ground-based and Airborne Instrumentation for Astronomy, 62695R (27 June 2006); doi: 10.1117/12.671728; https://doi.org/10.1117/12.671728
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