We recently made the first observation of the optical trapping of neutral atoms by the forces of resonance-radiation pressure. We present an updated view of our experimental efforts on optical trapping.
We report the first observation of optically trapped atoms. Sodium atoms cooled below ${10}^{\ensuremath{-}3}$ K in "optical molasses" are captured by a dipole-force optical trap created by a single, strongly focused, Gaussian laser beam tuned several hundred gigahertz below the D1 resonance transition. We estimate that about 500 atoms are confined in a volume of about 103 \ensuremath{\mu}m3 at a density of 1011-1012 ${\mathrm{cm}}^{\ensuremath{-}3}$. Trap lifetimes are limited by background pressure to several seconds. The observed trapping behavior is in good quantitative agreement with theoretical expectations.
In ordinary optics one exploits the interaction of radiation with matter to manipulate beams of light. One can also turn the tables and control beams of charged or neutral material particles through their interaction with light. There are deep analogies and similarities between these two sorts of optics, even though they involve very different kinds of interactions between matter and radiation. Perhaps one can exploit every such interaction for some kind of “optics”—controlling beams of photons or massive particles. In this article we will describe recent developments in the laser optics of atomic beams—how experimenters are using the radiation pressure of laser light to manipulate neutral atoms.
The forces felt by atoms when illuminated with resonant radiation can reduce their velocity dispersion and confine them in a region of space for further probing and experimentation. The forces can be dissipative or conservative and allow manipulations of the external degrees of freedom of atoms and small neutral particles. Laser cooling and trapping is now an important tool for many spectroscopic studies. It enhances the density of atoms in phase space by many orders of magnitude reducing the need of large samples. These lecture notes review the fundamental principles of the field and show some of the applications to the study of the spectroscopy of radioactive atoms. 1