Raman-induced resonance imaging of trapped atoms

This dissertation describes the development of the first neutral atom trapping apparatus at Duke University and Raman induced resonance imaging of trapped atoms-an imaging technique which provides three-dimensional information about the atomic spatial distribution in the trap. The design and operating principles of the ⁶Li atom source, laser sources, multi-coil Zeeman slower, and magneto-optic trap used in the experiment are explained. Using Raman induced resonance imaging, the atomic spatial distribution in the magneto-optic trap is imaged with 12 μm resolution. Changes to the experiment will yield a resolution of 5 μm-rivaling the best resolution achieved in previous two-dimensional imaging experiments-without the expense of large aperture optics and high resolution cameras. The position distribution of atoms is acquired by inducing Raman transitions between lithium's ground state hyperfine levels. The quadrupole magnetic field of the MOT causes the Raman transition strength and Raman resonance frequency to vary with position. By measuring the response of the atomic distribution at different Raman pulse frequencies, a spectrum is obtained which depends on the position distribution of the atoms. Previous images of trapped atoms used CCD cameras to record fluorescence or phase contrast images of the atomic spatial distribution. Because the CCD camera measures only two-dimensional information, the entire depth of the trap was averaged onto a single plane. In Raman induced resonance imaging of the MOT, the number of atoms in concentric ellipsoidal shells is measured. Consequently, Raman induced resonance imaging is ideally suited for probing small centrally located density variations within high density atomic spatial distributions, a regime in which two-dimensional imaging with a camera is unsuitable. In this dissertation, Raman induced resonance imaging is used to determine the size of the atomic distribution and it's offset relative to the MOT's magnetic field zero point. The center of the atomic cloud is found to be substantially shifted from the magnetic field zero point of the trap. In addition, the work presented here significantly advances the development of single-shot Raman transient imaging techniques that will have wide applications to fundamental measurements of ultracold trapped atoms.