12 September 2014 Development of wideband spectral dispersers for exoplanetary science: comparative study of material, design, and fabrication
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Abstract
We present the development of wideband spectral dispersers of which the primary scientific objective is the characterization of the atmospheres of exoplanets, including the challenge of detecting biomarkers. A disperser comprising a prism with a grating pattern on its surface provides simultaneous wideband coverage with low spectral resolution (R ≥ 300). The optics is simple, compact, and contains no moving parts. A comparative study of 21 materials for the disperser was carried out for use in the optical, near-infrared, and mid-infrared wavelength regions. KRS-5, CdZnTe, ZnS LiF, Sapphire, and S-TIH11 were selected, and designs of the optics for single-channel wideband spectrometers using the selected six materials were considered. Then, trial designs of the multi-channel spectrometers were carried out taking the properties of the detectors into consideration. The 3-channel design covers the wavelength region of ∼0.2−23 μm using a CCD detector, an InSb detector, and a Si:As detector. The 2-channel design covers ∼0.4−23 μm using a HgCdTe detector and a Si:As detector. A fabricated ZnS disperser is shown together with a CsI subprism which compensates for the optical axis. The application of defocusing, high dispersion spectroscopy, extension to the UV wavelength region, and the combination of the disperser with future space telescopes are discussed.
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Keigo Enya, Naofumi Fujishiro, "Development of wideband spectral dispersers for exoplanetary science: comparative study of material, design, and fabrication", Proc. SPIE 9193, Novel Optical Systems Design and Optimization XVII, 91931H (12 September 2014); doi: 10.1117/12.2061684; https://doi.org/10.1117/12.2061684
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