Sideband cooling

Optical sideband cooling is quite analogous to the Doppler cooling by photon recoil discussed in Sect. 9.1. The only difference is that the confinement of the ion within the trap leads to discrete energy levels of the oscillating ion, whereas the translational energy of a free atom corresponds to a continuous absorption spectrum within the Doppler width. 

Optical sideband cooling was demonstrated for Mg+ ions in a Penning trap [1227,1228] and for Ba+ ions in an RF quadrupole trap [1229]. The Mg+ ions were cooled below 0.5 K on the is Si/2- ip P3/2 transition by a frequency-doubled dye laser at X = 560.2 nm. The vibrational amplitude of the oscillating ions decreased to a few microns. With decreasing temperature the ions are therefore confined to a smaller and smaller volume around the trap center. 

W. Neuhauser, M. Hohenstatt, RE. Toschek, H. Dehmelt, Optictil sideband cooling of visible atom cloud confined in a parabolic well. Phys. Rev. Lett. 41,233 (1978)... 

If several ions are trapped in an ion trap and are cooled by optical sideband cooling, a phase transition may occur at the temperature Tc where the ions arrange into a stable, spatially symmetric configuration like in a crystal [14.88-14.91]. The distances between the ions in this Wigner crystal are about 10 — 10 times larger than those in an ordinary ion crystal such as NaCl. 

The lo- error includes uncertainties due to magnetic field extrapolations (0.40) and to the second-order Doppler shift (0.40), and could be diminished by better shielding of the magnetic field and by optical sideband cooling. The result of a classical optical pumping experiment was... 

Neuhauser, W., Hohenstatt, M., Toschek, P., and Dehmelt, H. (1978). Optical sideband cooling of visible atom cloud confined in particle well. Physical Review Letters, 41, 233-236. 

Vuletic, V., Chin, C., Kerman, A. L, and Chu, S. (1998). Degenerate Raman sideband cooling of trapped cesium atoms at very high atomic densities. Physical Review Letters, 81, 5768-5771. 

Optical sideband cooling has been used to cool Mg II ions to temperatures... 

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