Laser Cooling and Trapping

Zongze Li

As a matter of fact, the laser cooling and trapping has already been widely used in various fields in advanced atoms controlling. With this in mind, this study gives a systematical analysis of the principle of laser cooling and trapping, and the development of them in the recent years. To be specific, this study will discuss the applications that has invented in the recent year based on the laser colling and trapping (especially for the state-of-art facilities), and makes a comparison between the concepts of laser cooling and laser trapping accordingly. Then, based on the analysis and evaluations, the limitations of laser cooling and laser trapping have been shown, and the future outlooks are also claimed and demonstrated as well. To sum up, the study concludes by discussing the limitations of these techniques, and gives some methods to solve these issues. Overall, these results shed light on guiding further exploration of laser cooling and trapping.

Vladilen S Letokhov

Abstract One of the most remarkable achievements of laser control is the manipulation of atomic particles, their velocities, positions, etc., which is referred to as laser cooling and laser trapping . These two effects are interrelated and usually prove effective when used jointly. That this is so one can see by considering as an example the laser cooling of trapped ions and the laser trapping of laser-cooled neutral atoms (Fig. 5.1). The sequences of processes in these two situations are directly opposite. Ions can easily be trapped in an electromagnetic trap of large depth (Paul 1990) and then be cooled for a long time by laser radiation (sideband cooling) (Wineland and Dehmelt 1975; Dehmelt 1990). Neutral atoms are first slowed down and cooled by laser radiation down to millikelvin temperatures, and only then confined in an optical trap. Trapped atoms can further be cooled to microkelvin temperatures. The present chapter and Chapter 6 consider the cooling and trapping of neutral atoms, the present chapter concentrating on their cooling, and Chapter 6 on trapping. But it would be reasonable first to familiarize the reader with the history of the early ideas in this field that eventually led to the advent of a new domain of physics—the physics of ultracold atoms and molecules (Chapters 7 and 8).

Jean-Louis Basdevant, Jean Dalibard

Charles S. Adams, Ifan G. Hughes

Ralph G. DeVoe, John A. Hoffnagle, Richard G. Brewer

Several groups have recently used laser cooling to produce ordered arrays of ions, ion crystals, in rf quadrupole ion traps (Paul traps). Laser cooling has been understood using previous theories which ignore ion micromotion and replace the oscillating rf trap potential with a static pseudopotential. We show that in recent experiments, ion micromotion can exceed one wavelength of the cooling radiation and that the resulting Doppler shifts can transform laser cooling into laser heating. Changes in trap voltage, ion position, and laser intensity can all reverse the sign of laser cooling. This, together with ideas of deterministic chaos, can lead to a reinterpretation of experiments on ion crystals. The recognition that effects previously attributed to an experimental artifact, rf heating, may actually be due to a failure of laser cooling opens the door, on the one hand, to precise theories of phase transitions and, on the other, to improved cooling techniques that can permit the creation of larger ion crystals.