Coherent two-photon spectroscopy for narrow linewidth atomic clocks in thermal alkali vapours

The goal of this work is to take a step change in our approach towards a low SWaP atomic clock with excellent short-term stability (~10-13 in one second) and long-term accuracy (~10-15). The project will harness features of the current state-of-the art systems; firstly we will use two-photon probing of an optical transition allowing for a high-Q system. Secondly, we will use optical-dense thermal gases of alkali atoms that are key to CSACs (chip-scale atomic clocks).

Work to be undertaken:
- Use of commercially-available, pulsed 778-nm lasers for interrogation of the weakly-forbidden 5S1/2 - 5D5/2 in rubidium.
- Connection with compact optical frequency combs.
- Interrogation components into a single, compact system.

Benefits:
Two-photon probing of an optical transition crosses the boundary between microwave and optical clocks, and is a unique opportunity to bridge the divide in sensitivity of approximately three-orders of magnitude that currently exists between them.

The use of pulsed lasers enables coherent enhancement of the clock-state interrogation. This is in addition to allowing the efficient use of commercially available telecoms lasers and components.

Moving to thermal atoms removes the needs for laser cooling.