Combining red and blue detuned optical potentials to form a Lamb Dicke trap for a single neutral atom.
We propose and demonstrate a scheme for strong radial confinement of a single 87 Rb atom by a bichromatic far off resonance optical dipole trap (BFORT) The BFORT is composed of a blue detuned Laguerre Gaussian LG01 beam and a red detuned Gaussian beam. The atomic oscillation frequency measurement shows that the effective trapping dimension is much sharper than that from a diffraction limited microscopic objective. Theory shows that the added scattering rate due to imposing blue detuned light is negligible when the temperature of the single atoms is close to ground state temperature. By carrying out sub Doppler cooling, the mean energy of single atoms trapped in the BFORT is reduced to 15 1 mK. The corresponding mean quantum number of radial vibration n is about 1.65, which satisfies the Lamb Dicke regime. We conclude that the BFORT is a suitable Lamb Dicke trap for further cooling a single neutral atom down to the ground state and for further application in quantum information processing.
Optics express