title: Spectral uniformity of two- and four-level diffractive optical elements for spectroscopy.
abstract: We present simulations and characterization of gold coated diffractive optical elements (DOEs) that have been designed and fabricated in silicon for an industrial application of near-infrared spectroscopy. The DOE design is focusing and reflecting, and two-level and four-level binary designs were studied. Our application requires the spectral response of the DOE to be uniform over the DOE surface. Thus the variation in the spectral response over the surface was measured, and studied in simulations. Measurements as well as simulations show that the uniformity of the spectral response is much better for the four-level design than for the two-level design. Finally, simulations and measurements show that the four-level design meets the requirements of spectral uniformity from the industrial application, whereas the simulations show that the physical properties of diffraction gratings in general make the simpler tw level design unsuitable.
authors.affiliation: Department of Physics, University of Oslo, Center for Materials Science and Nanotechnology, Blindern, Norway. hallvard.angelskar@fys.uio.no
authors.forename: Hallvard
authors.initials: H
authors.lastname: Angelskår
authors.forename: Ib-Rune
authors.initials: IR
authors.lastname: Johansen
authors.forename: Matthieu
authors.initials: M
authors.lastname: Lacolle
authors.forename: Håkon
authors.initials: H
authors.lastname: Sagberg
authors.forename: Aasmund S
authors.initials: AS
authors.lastname: Sudbø
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation*