SIMBAD references

We 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.