title: Alignment-free characterization of 2D gratings.
abstract: Fast characterization of 2D gratings is demonstrated using a Fourier lens optical system and a differential optimization algorithm. It is shown that the grating-specific parameters such as the basis vectors and the angle between them, along with the alignment of the sample, such as the rotation of the sample around the x, y, and z axis, can be deduced from a single measurement. More specifically, the lattice vectors and the angle between them have been measured, while the corrections of the alignment parameters are used to improve the quality of the measurement and, hence, reduce the measurement uncertainty. Alignment-free characterization is demonstrated on a 2D hexagonal grating with a period of 700 nm and a checkerboard grating with a pitch of 3000 nm. The method also can be used for automatic alignment and in-line characterization of gratings.
authors.forename: Morten Hannibal
authors.initials: MH
authors.lastname: Madsen
authors.forename: Pierre
authors.initials: P
authors.lastname: Boher
authors.forename: Poul-Erik
authors.initials: PE
authors.lastname: Hansen
authors.forename: Jan Friis
authors.initials: JF
authors.lastname: Jørgensen