Date of Award
Doctor of Philosophy (PhD)
Steven R. Jefferts
For many years atomic fountains provided the most accurate measurements ever made: up to sixteen decimal places of the Cesium ground state hyperfine splitting. This thesis project sought to bring this unprecedented precision, afforded by atomic fountains, into a transportable package. Such a devise would be valuable to many applications involving precise timing and frequency comparisons. For example, the active field of optical clock research could benefit from a stable and robust transportable frequency reference, since frequency comparisons at the sixteenth decimal place are presently highly impractical beyond distances of 100 km. Outside of the scientific community the applications become more numerous. This is especially true if further refinement culminated in a commercially available version of a transportable atomic fountain.
The bulk of this research concerned the development of a suitable laser system. A design based on electronically phase-locking independent slave lasers to a single master laser would provide a simple, robust, compact, and low-power system for operating an atomic fountain. We investigated newly available distributed feedback (DFB) and distributed Bragg reflecting (DBR) diode lasers, and found each to be lacking in one or another critical factors. The DFB laser diodes proved to have unreliable lifetimes, unacceptable for an atomic fountain that is meant to be robust and reliable. The DBR lasers have an internal phase delay that severely limits the achievable phase coherence between the lasers, and this was found to be detrimental to the requisite sub-Doppler laser cooling in a fountain. We present measurements characterizing the limitations of the current system, and propose solutions for further investigation.
Kunz, Paul David, "Towards a Transportable Atomic Fountain" (2013). Physics Graduate Theses & Dissertations. 94.