26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Theoretical and Practical Developments of a Compact, Efficient Dual-Colour Two-Photon Rubidium Optical Frequency Standard

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Invited talk AIP | Atomic and Molecular Physics (ATMOP)

Speaker

Dr Sarah Scholten (Institute for Photonics and Advanced Sensing, Adelaide University)

Description

Atomic clocks provide precise timing signals critical to modern infrastructure including Communication networks, power infrastructure, and positioning, navigation and timing (PNT) services such as the Global Navigation Satellite System (GNSS). While these clocks have traditionally used microwaves to drive atomic transitions, recent research efforts have utilised lasers due to the promise of higher potential performance. This next generation of optical atomic clocks must balance performance, system complexity, and Size, Weight, and Power consumption, as well as component cost (SWaP-C) to be competitive replacements for their older microwave counterparts.

The two-photon 5S$_{1/2}$ $\rightarrow$ 5D$_{5/2}$ transition in rubidium-87 is a promising clock candidate, with the transition easily accessible by frequency doubling well-developed and robust telecommunications-band fibre lasers in a simple Doppler-free configuration. In particular, the dual-colour excitation method, utilising both 776nm and 780nm light, provides an extra degree of freedom in the detuning from the intermediate 5P$_{3/2}$ state, providing resonant enhancement of the atomic transition rates compared to the commonly seen dual 778nm photon excitation scheme. However, the decreased intermediate state detuning of ~1.5GHz compared to the single-colour excitation scheme’s ~1THz comes at the cost of increased light shift contributions to frequency instability in the clock when considering similar optical powers.

A comprehensive understanding of the 5S$_{1/2}$ $\rightarrow$ 5D$_{5/2}$ transition is therefore required to extract the full potential of the dual-colour scheme. Here, we present our developments informing the next generation of miniaturised, deployable dual-colour two-photon rubidium optical atomic clocks. We will discuss the leading long-term performance rubidium two-photon optical atomic clock, its fully autonomous performance at field trials, and commercialisation progress. Miniaturisation efforts including the exploration of heterogeneously integrated photonic integrated circuit (PIC) lasers, PICs, and Micro-Electro-Mechanical Systems (MEMS) rubidium cells will be discussed, as well as experimental and theoretical explorations on the effects of light shifts on clock performance.