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

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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.