Abstract-Direct frequency-comb-driven Raman transitions in the terahertz range

Cyrille Solaro, Steffen Meyer, Karin Fisher, Michael V. DePalatis, Michael Drewsen

https://arxiv.org/abs/1712.07429

We demonstrate the use of a femtosecond frequency comb to coherently drive stimulated Raman transitions between terahertz-spaced atomic energy levels. More specifically, we address the 3d 2D3/2 and 3d 2D5/2 fine structure levels of a single trapped 40Ca+ ion and spectroscopically resolve the transition frequency to be νD=1,819,599,021,534±8 Hz. The achieved accuracy is nearly a factor of five better than the previous best Raman spectroscopy, and is currently limited by the stability of our atomic clock reference. Furthermore, the population dynamics of frequency-comb-driven Raman transitions can be fully predicted from the spectral properties of the frequency comb, and Rabi oscillations with a contrast of 99.3(6)\% and millisecond coherence time has been achieved. Importantly, the technique can be easily generalized to transitions in the sub-kHz to tens of THz range and should be applicable for driving, e.g., spin-resolved rovibrational transitions in molecules and hyperfine transitions in highly charged ions.