6 July 2006 High efficiency germanium immersion gratings
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Abstract
We have fabricated several germanium immersion gratings by single crystal, single point diamond flycutting on an ultra-precision lathe. Use of a dead sharp tool produces groove corners less than 0.1 micron in radius and consequently high diffraction efficiency. We measured first order efficiencies in immersion of over 80% at 10.6 micron wavelength. Wavefront error was low averaging 0.06 wave rms (at 633 nm) across the full aperture. The grating spectral response was free of ghosts down to our detection limit of 1 part in 104. Scatter should be low based upon the surface roughness. Measurement of the spectral line profile of a CO2 laser sets an upper bound on total integrated scatter of 0.5%.
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Paul J. Kuzmenko, Paul J. Kuzmenko, Pete J. Davis, Pete J. Davis, Steve L. Little, Steve L. Little, Liesl M. Little, Liesl M. Little, Jay V. Bixler, Jay V. Bixler, } "High efficiency germanium immersion gratings", Proc. SPIE 6273, Optomechanical Technologies for Astronomy, 62733T (6 July 2006); doi: 10.1117/12.670565; https://doi.org/10.1117/12.670565
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