Alignment-free characterization of 2D gratings.

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.