Dark State Physics

See also Publications on this topic, also listed below

There are many different effects in the quantum domain of optical manipulation of atoms, especially those connected with dark states. A few years ago we predicted the existence of dark states even in a simple two level atom, without the complications of internal quantum numbers and polarized light beams. This prediction has recently been verified by our observation of VSCPT in He* on the l = 389 nm transition. Adequate description of this phenomenon requires that the atomic center-of-mass motion be included in the total Hamiltonian that describes the system, and thus it is a purely quantum effect.

The two level system is produced using circularly polarized light to drive the J = 1 ® 2 transition to the 3³P state of helium. This most primitive case of VSCPT exposes its simple nature as a special kind of quantum interference, and demonstrates the presence of VSCPT in a system that has no truly dark state. It is readily observed for this particular transition because the ratio of the recoil frequency to the natural linewidth is 0.22, two orders of magnitude larger than for most laser cooling experiments. Moreover, as a result of a numerical accident, laser cooling is totally absent in the usual J = 1 ® 1 transition used in previously described VSCPT experiments, but our trapped state is fed by Doppler cooling on this J = 1 ® 2 transition. It is unusually effective in this case because of the large recoil (the recoil and Doppler temperatures are nearly equal).

Publications:

"Bichromatic Velocity-Selective Coherent Population Trapping" (M. Doery, E. Vredenbregt, R. Gupta, T. Bergeman, and H. Metcalf) Phys. Rev. A51, 2334 (1995).

"Population Accumulation in Dark States" (M. Doery, M. Widmer, J. Bellanca, W. Buell, T. Bergeman, and H. Metcalf), Phys. Rev. A52, 2295 (1995).

"High Velocity Dark States in Velocity Selective Coherent Population Trapping" (M. Widmer, M. Doery, J. Bellanca, W. Buell, T. Bergeman, and H. Metcalf) Phys. Rev. A53, 946 (1996).

"Measurement of Force-Assisted Population Accumulation in Dark States" (M. Widmer, M-J. Bellanca, W. Buell, M. Doery, E. Vredenbregt, and H. Metcalf) Opt. Lett.21, 606 (1996).

"Laser Cooling as a Form of Optical Pumping", (H. Metcalf), Physica Scripta T70, 57 (1997)."Dark States and deBroglie Wave Optics", (H. Metcalf), Acta Physica Polonica, 93, 147, 1997.

Abstracts

"Population Accumulation in Dark States" (M. Doery, E. Vredenbregt, M. Widmer, M. Bellanca, T. Bergeman, W. Buell, and H. Metcalf) Bull. Am. Phys. Soc. 40, 1313 (1995) TP17.

"New Phenomena in Dark States", (M. Widmer, M. Doery, M. J. Bellanca, W. Buell, T. Bergeman, and H. Metcalf), Bull. Am. Phys. Soc. 40, 1312 (1995) TP16.

"Laser Cooling in the Quantum Domain: Shedding New Light on Dark States", (M. Widmer, M. Doery, M-J. Bellanca, F. Chi, W. Buell, E. Vredenbregt, and H. Metcalf) Abstracts of CQO7, Rochester, 1995, W4A26.

"Sub-Recoil Temperatures of Velocity Selective Resonances in Metastable Helium", (J. Hack, M-J. Bellanca, L. Liu, and H. Metcalf), Bull. Am. Phys. Soc. 43 (1998).

"Velocity-Resonant Precession" (M-J. Bellanca, L. Liu, T. Bergeman, G. Raithel, and H. Metcalf), Bull. Am. Phys. Soc. 44, 725 (1998), NP01-23.