Atomic-beam propagation in a two-dimensional standing wave of light: A numerical analysis based on a particle-optics

We study the propagation of an atomic beam flow in an optical potential gen erated by a two-dimensional (2D) standing wave produced by two interfering laser beams with a frequency that is close to the resonant frequency of the propagated atoms. We extended the equations of motion of an atom in a ligh t field to three-dimensional (3D) coordinate system and calculated the 3D t rajectories of chromium atoms that are thermally evaporated and deflected b y the gradient force of the standing wave laser field. The polarization and polarity of detuning of the frequency of the interfering beams are varied to study the formation of chromium atoms on a substrate. Our results show t hat a combination of parallel polarization and positive detuning forms a 2D grid structure. The rest of the combination of polarization and polarity o f detuning yields a 2D array of point structures. An optimum size of the po int structure with a diameter of approximately 50 nm can be formed with an orthogonal polarization and positive detuning of the laser frequency.