Laser trapping, cooling and sensing of atoms and molecules with nanostructured surfaces

The study and manipulation of atoms and molecules has until recently nearly always been performed upon mobile and energetic species. Yet, as in so many fields, measurement and manipulation could be performed with far greater precision and finesse if the subject were confined and immobilized. Despite many techniques which focus on the slowest species, most measurements and virtually all reactions of atoms and molecules are performed on thermal distributions. The consequences for fundamental studies, processing and sensing are a finite interaction time and a moving, randomly orientated sample.Laser tweezers and Doppler cooling techniques use the radiation pressure exerted by a stream of photons to slow and capture a limited range of atoms. Pinned down and virtually stationary, the atoms can be examined and manipulated like never before. Deterministic quantum mechanics dominates their behaviour; collisions are reversible; and molecules can be formed and then broken with exquisite remote control. Even in these early days, a wide range of technological exploitations has been proposed, from metrology to sensing and information processing. Unfortunately, only single, tiny traps are usually possible, and, because the cooling process only works with a limited range of species, most atoms and all molecules that enter the trap retain enough kinetic energy to leave shortly after.We propose to use nanofabrication techniques, developed in Southampton, to produce arrays of concave mirrors whose foci, when illuminated with a laser, will each become a tiny trap. Such arrays offer to store many more species than a single trap, and each trap can easily be distinguished under a microscope. Confining species within a few wavelengths of a surface allows new interactions and techniques that increase the trap strength and enhance the sensitivity with which the species may be detected and observed. The extent and proximity of the surface also presents exciting new mechanisms for cooling a far wider range of species than previously possible. This research will investigate a range of trapping and cooling geometries, with the ultimate aim of extending to molecules the control currently limited to atomic samples of just a small number of elements.