Abstract
ABSTRACTWe have developed a special grating capable of producing an echellogram (a spectrum arranged in raster form) in the 30th or even higher order in the near‐infrared wavelength region. The grating substrate is made of an aluminum alloy that has been carved mechanically with a high‐precision shaving machine. The optical efficiency, measured with a special spectrophotometer at about 2 μm, is ∼70%. The diffuse light component, possibly attributable to scattering on the grating surface, has been estimated to be at most ∼5% when the grating is incorporated in an actual spectrograph system. The measured efficiency of the fabricated grating is compared with that given by a numerical analysis. The comparison shows remarkable agreement in both the optical efficiency and the distribution of energy diffracted to various orders.
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