Atom reflection from an evanescent wave mirror: measurement of the van der Waals force and demonstration of atomic diffraction

This thesis describes two experiments using an evanescent wave mirror. The mirror is based on the dipole force due to the interaction between the atoms and an evanescent wave, created by total internal reflection of a laser beam in a prism. These two experiments show that the atoms can be used as a probe of the near field of the surface of the prism. The first experiment is a measurement of the van der Waals force between a rubidium atom in the ground state and a dielectric wall. During reflection, the atoms are close to the dielectric surface (∼ 50 nm) and are sensitive to the attractive van der Waals force due to the presence of the wall. The experiment consists in measuring the dipole force required to balance the van der Waals force. It also shows the crucial role of the van der Waals force in an atomic mirror: on the one hand, the reduction of the potential height by a factor of three and on the other hand the modification of the shape of the total reflecting potential. The second experiment describes atomic diffraction at normal incidence on a spatially modulated mirror, created by a partially standing evanescent wave. The diffraction process is due to the phase modulation of the de Broglie wave and appears for very weak modulation. It is analogous to Raman-Nath diffraction in traditional optics. The study of the populations of the different orders of diffraction as a function of modulation depth quantitatively confirms a theoretical treatment. (author)