Two-dimesional atomic crystal bound by light

We have observed the vibrational levels of rubidium atoms spatially confined in two dimensions by two crossed optical standing waves (oriented along the x and y axes) with mutually orthogonal linear polarization (in the x-y plane). When the two standing waves oscillate with a 90^ time phase delay, the atoms are confined by dipole forces to the intensity maxima forming a two-dimensional collimated array of linear de Broglie waveguides, spaced by half an optical wavelength. When the standing waves oscillate in phase no vibrational energy structure can be observed.