New Tools for Precision Measurement and Quantum Science with Narrow Linewidth Optical Transitions

In my thesis work, I have explored a variety of ways in which narrow linewidth optical transitions can be utilized to extend the capabilities of precision measurement and quantum science. These tools include non-destructive atom counting techniques that may enhance the performance of optical lattice clocks, a novel form of cavity enhanced atomic spectroscopy appropriate for laser frequency stabilization, a new form of laser cooling with reduced reliance on spontaneous emission, several methods for enhancing the sensitivity of proposed atomic gravitational wave detectors, a newly observed form of cavity-mediated spin-spin interactions, and a new class of laser based on optical superradiance from narrow and ultra-narrow linewidth transitions. As part of the superradiant laser project, we have demonstrated the most precise active absolute frequency reference realized to date, which still has great potential for improvement. Many of these tools involve coupling atoms to an optical cavity, a field known as cavity quantum electrodynamics, or cavity QED. In my thesis work, a key focus was the extension of cavity QED techniques into the new regime of coupling large ensembles of atoms to a cavity using narrow linewidth optical transitions (in contrast to the previously explored regimes of microwavefrequency transitions or broad-linewidth optical transitions). To this end, I constructed a new experiment to couple an ensemble of atoms to an optical cavity using two optical transitions in atomic strontium, one with a narrow 7.5 kHz linewidth, and another with an ultra-narrow 1 mHz linewidth. This new system has allowed us to access a unique new regime of cavity QED, and a wealth of interesting and useful applications.