AAS 207th Meeting, 8-12 January 2006
Session 173 Instrumentation: Ground Based or Airbourne
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

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[173.13] Extremely High Dispersion Silicon Immersion Grating for Hunting Life-bearing, Earth-like Planets around M Dwarfs in the Near-IR

D. McDavitt, J. Ge, B. Zhao, S. Miller (University of Florida)

Hunting Earth-like, life-bearing planets around M dwarfs requires a high resolution spectrometer with an R = 30,000 at large ground-based telescopes. This is an enormous challenge for traditional designs using commercial echelle gratings since the cryogenic instrument becomes too large. A newly developed silicon immersion grating at the University of Florida (UF) offers an emerging opportunity for building a high resolution, high efficiency, but compact cross-dispersed grating spectrometer with a large wavelength coverage required for detecting Earth-like planets around low mass M dwarfs for the first time. High dispersion and large wavelength coverage become possible due to the extremely high refractive index of silicon (n=3.4) in the IR and silicon's ability to be formed into coarse grooves.

At UF, cross-dispersed R = 42,000 near-IR spectroscopy has been produced with a newly developed silicon immersion grating. This was achieved in a spectrometer with only a 25 mm diameter collimated beam, a 100 \mum core fiber, a 54.7 deg blaze angle and a 16/mm groove density (or 62.3 \mum period). This is the first time that a silicon immersion grating has ever produced IR spectroscopy with an R = 10,000. The cross-dispersed spectral format with an R = 42,000 is the highest obtained with gratings on the ground.

We acknowledge the support from NSF AST-0451408, NASA NNG05G321G and NNG05GR41G, and the University of Florida.

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