Breakdown of Babinet's principle in atom optics

Abstract

We observe the breakdown of Babinet's principle in quantum reflection of helium atoms from diffraction gratings. Helium atom beams are reflected and diffracted by gratings of complementary geometry at grazing incidence angles of a few mrad. According to Babinet's principle the diffraction intensities are expected to be identical for corresponding grating pairs. However, our data reveal significant deviations for conditions when either incident or diffracted beams propagate close to the grating surface. The breakdown of Babinet’s principle is also severe near Rayleigh conditions where a new spectral order emerges from the grating surface. At these conditions, the incident and diffracted helium beams are strongly affected by the dispersive interaction between the atoms and the grating surface. We therefore attribute the breakdown to atom-surface interactions and emerging beam resonances.