Accurate calibration of grating pitch

A current issue insufficiently addressed in nanometrology is the accurate characterization of calibrators with nanoscale features. Gratings are such calibrators and their pitch is one of the features that are used for calibration purposes. In this article the classic method of determining the gratings pitch from the measurement of the angular position of the refracted orders is used. To ensure traceability one has to relate the measurements to the wavelength of a frequency stabilized laser and that can be accomplished by using such a laser as the light source in the experiment. The method is shown to have adequate accuracy for nanometrological needs. A salient feature of the method revealed by error analysis is the fact that the absolute estimation error decreases with the pitch, making the method especially suited for nanometrology. The modern use of the method rather than the method itself is the element of novelty here, of a technological rather than scientific nature.