Optical tailoring of spatial distribution of the BEC and non-degenerate cold atoms. Non-periodic optical lattice

Full text: Optical lattices are the instruments of great importance in many fields of atomic physics like manipulating of neutral particles, quantum computing, etc. The common method of getting a periodic optical lattice is to use the interference of two or more laser beams which form an array of periodic light-shift potentials. We demonstrate a new method of creating an optical lattice of either non-degenerate cold atoms or Bose-Einstein condensates. The lattice is obtained when the cloud of cold atoms is illuminated by a focused, off-resonant laser beam split into several beams by a diffraction process. The resulting lattice is non-periodic. In our experiment we used 87Rb atoms trapped in the magnetic trap of the Ioffe-Pritchard type. This is an anisotropic and harmonic trap characterized by frequencies: radial ωr = 2 π · 137 Hz and axial ωa = 2 π · 12 Hz. The laser beam of a frequency close to the D1 line of 87Rb was used in the experiment. We analyze the evolution of that kind of lattice either in a magnetic trap or during time of flight after the atoms are released from the trap. Due to interactions between atoms and near resonant light the characteristic regular structure of atoms appears. We characterize the basic properties of this structure in two cases of a nondegenerate atom cloud and a BEC. In particular, we analyze the effect of the laser frequency on the formation process of optical lattice. Our method can be another way of studying phenomena where an optical lattice is a necessary instrument. The presented method of creating the optical lattice might be an alternative to the standard counter-propagating laser beams method. (author)