AAS 203rd Meeting, January 2004
Session 38 Observation and Instrumentation : Optical
Poster, Tuesday, January 6, 2004, 9:20am-6:30pm, Grand Hall

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[38.07] Very High Resolution IR Spectroscopy with a Silicon Anamorphic Immersion Grating

J. Ge, D. McDavitt, J. Wang, S. Miller (Penn State)

We report new results from high resolution IR spectroscopy using a silicon anamorphic immersion grating with a spectral resolution of R = 220,000 in the near IR. This grating was developed at Penn State through a new grating technique based on photolithography and tetramethyl ammonium hydroxide (TMAH) anisotropic chemical etching. The grating has an 80x50 mm2 etched grating area, a 63.5 deg blaze angle and a 5.4 l/mm groove density (or 185 \mum) on a 30 mm thick silicon substrate. The groove density is about 4 times coarser than any existing commercial echelle gratings, allowing for a complete coverage of a cross-dispersed echelle spectrum on a 1kx1k IR array at R = 220,000 in the K band. Optical measurements reveal a high quality wavefront, with an rms error of 0.065 waves and the integrated scattered light is ~ 1% at 632.8nm. A prototype extremely compact cross-dispersed silicon immersion grating spectrometer with a 10 mm diameter collimated beam was built and tested with both artificial light sources and sun light. Initial R = 220,000 spectroscopy results will be presented.

This work was supported by NASA grants NGA5-12115, NAG5-11427, NSF AST-0138235 and the Penn State Eberly College of Science.

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