title: Analysis of multimask fabrication errors for diffractive optical elements.
abstract: As design algorithms for diffractive optical elements improve, the limiting factor becomes the fabrication process. It is hoped a better understanding of fabrication errors will allow elements with greater tolerance to be designed. This is important for high-power laser fiber coupling, where hot spots lead to failure. We model seven different fan-out gratings applying misetch, misalignment, and feature rounding. Our main findings are that misetch can lead to improved results, misalignment is strongly asymmetric, and both the pi and pi/2 masks can dominate misalignment. Rounding has a r(2) dependence and potentially can be incorporated into the design stage. Finally we present some experimental data for misalignment.
authors.affiliation: School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK. ajc4@hw.ac.uk
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Caley
authors.forename: Markus
authors.initials: M
authors.lastname: Braun
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Waddie
authors.forename: Mohammad R
authors.initials: MR
authors.lastname: Taghizadeh