The aim of DiALON is to investigate cooperative and multiple scattering of light in one dimension using optical nanofibres. Two complementary experimental approaches will be pursued: atoms trapped around an optical nanofibre and nanofibres perforated with nanoscopic holes. The question of the interplay between cooperative effects, based on Dicke super- and subradiance in extended dense ensembles and Anderson localisation of light, will be addressed. The special case of ordered atomic distributions will enable to establish connections to known results in condensed matter physics.
Atoms trapped in a 1D optical lattice created in the evanescent field surrounding an optical nanofibre are ideally suited to the study of cooperative and multiple scattering of the nanofibre-guided light. Subradiant states should be straightforwardly prepared because the atom-light interaction results in a driven timed Dicke state with a wavenumber exceeding the vacuum value. Concerning the free-space modes, this state will be sub- or superradiant, depending on the spatial period of the optical lattice. Regardless of this spatial period, the state is superradiantly coupled to the nanofibre mode. Disorder appears naturally in the system if the filling factor of the optical lattice sites is smaller than one. The trapping potential can, however, also be turned into a 1D tube along the nanofibre. The freely moving atoms will then realise a random 1D distribution, possibly leading to Anderson localisation of the fibre-guided light. In both cases, a total optical depth of the atomic ensemble on the order of 100 is experimentally accessible.
In a complementary experimental approach, we will explore a novel model system employing optical nanofibres with disordered nanoholes. This will present the advantage to let us choose at will the number and density of scatterers as well as their disorder and scattering properties, the latter being tunable via the nanohole parameters like width and aspect ratio.