Laser-cooled rubidium atoms have been trapped in a nondissipative optical lattice with a large lattice constant. The lattice potential is generated by the ac Stark shift in an infrared standing wave near 10.6 $\mu$m. The atoms are confined in steep potential wells with a periodicity of several micrometers. By modulating the potential depth we parametrically excite the atoms and measure their vibrational frequencies.

• Received 8 August 1997

DOI:https://doi.org/10.1103/PhysRevA.57.R20