Quantum optics close to surfaces: brief description

Atoms close to solid surfaces have become omnipresent in laser cooling and trapping as well as in near-field optics. Atom-surface interactions determine both the internal and external atomic dynamics and hence the physical quantities measured in these fields. These interactions have been studied for thermal atoms and have to be reconsidered in view of recent experimental refinements (low atomic energies and accurate position control).

Long range

The long-range part of the atom-surface interaction (mediated by the electromagnetic field) determines the radiative properties of an atom in the near-field of a surface [1]. We have elaborated an analytical theory to describe level shifts and lifetimes as a function of the position close to simple surfaces, like gratings. The long-range interaction also influences the center-of-mass motion in the vicinity of the surface. Surface roughness distorts the optical potential and broadens the reflected atomic beam [2], which may ultimately lead to a novel type of surface analysis using neutral matter waves.

Short range

Surface interactions at short range lead to surface adsorption and determine the loss rates for atom traps close to surfaces [3]. We propose to generalize the master equation [4] describing the adsorption dynamics to the low energy domain where quantum corrections are expected to lead to a nonzero elastic reflection probability [5]. The atomic center-of-mass motion is also relevant for atomic lithography schemes [6] because it determines the lateral resolution of structures deposited on a substrate.
  1. L. Novotny; Appl. Phys. Lett. 69, 3806 (1996).
  2. C. Henkel, K. Moelmer, R. Kaiser, N. Vansteenkiste, C. I. Westbrook, A. Aspect; Phys. Rev. A 55, 1160 (1997).
  3. T. Pfau, J. Mlynek; OSA Trends in Optics and Photonics Series 7, 33 (1996).
  4. R. Brako, D. M. Newns; Surf. Sci. 117, 42 (1982).
  5. C. Henkel, C. I. Westbrook, A. Aspect; J. Opt. Soc. Am. B 13, 233 (1996);

  6. B. Segev, R. Côté, M. G. Raizen; Phys. Rev. A 56, 3350 (1997).
  7. S. Nowak, T. Pfau, J. Mlynek; Appl. Phys. B 63, 203 (1996).

Related publications (abstracts available: click on the title)

Atom optics

Put an atom into a light field nearly resonant to an atomic transition frequency, and the atom will be subject to radiative forces. The atomic motion can be manipulated in various ways by playing with the light frequency, its polarization and its spatial intensity distribution. One can make lenses, mirrors, and diffraction gratings for atomic beams: light is the ``optical instrument'', and the atoms are the ``beam''.

A mirror for atoms

Take the interface between a dielectric prism and  the vacuum. Reflect a laser beam inside the dielectric in such a way that total internal reflection takes place. There is no beam transmitted into the vacuum, but there is an evanescent wave that propagates parallel to the interface and decays exponentially into vacuum. With this light field, you can make a repulsive potential for atoms to prevent them from getting in contact with the dielectric body: a mirror.

Selected publications (abstracts available: click on the title)

C. Henkel, 20 july 1999.