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D.T. Jaffe, O. Ershov, J.P. Marsh (Dept. of Astronomy, UT Austin)
The high refractive index and good infrared transmission of silicon make it an excellent material for infrared grisms and immersion gratings. The use of these components can lead to very compact designs for IR spectrographs for large telescopes. We are using silicon micromachining techniques to produce diffraction gratings for near and mid-infrared devices. We report on progress in the optimization of the manufacturing process. Our best gratings currently have peak efficiencies of ~ 80% at 632 nm in ~360th order with minimal scattered light. We summarize the procedure for producing high quality devices and discuss the optical evaluation and electromagnetic modeling of the gratings. This work is supported by NASA grants NAG5-8858 and NAG5-9230 to the University of Texas at Austin.