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arXiv · 2505.13146

Exponential enhancement of sensitivity in Ramsey interferometry with optically thick ensemble of atoms

S. A. Moiseev·K. I. Gerasimov·M. M. Minnegaliev·I. V. Brekotkin·E. S. Moiseev
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Abstract

Ramsey interferometry is a cornerstone technique for precise measurement of time and frequency in modern clocks. The Ramsey experiments are typically done in optically dilute samples of atoms to improve homogeneity and avoid back-action of atoms on excitation pulses. In contrast to later belief, we predict and experimentally show that in optically thick samples with inhomogeneous broadening of resonant transition, the back-action can lead to the highly enhanced narrowing of Ramsey resonance. The linewidth narrowing and corresponding precision of the frequency measurement scale exponentially with an increase in optical depth of a sample and can reach the limits set by homogeneous broadening. We show that this effect is caused by a nonlinear interference of multiple echoes formed inside the atomic medium, which is experimentally confirmed with $^{167}\text{Er}^{3+}$ ions in $\text{Y}_2\text{SiO}_5$ crystal. Our findings open new opportunities for nonlinear high-resolution spectroscopy of resonant media and sensitivity enhancement in a new generation of solid state clocks.

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S. A. Moiseev, K. I. Gerasimov, M. M. Minnegaliev, I. V. Brekotkin, E. S. Moiseev. 2025-05-19. Exponential enhancement of sensitivity in Ramsey interferometry with optically thick ensemble of atoms. https://doi.org/10.1103/bqzh-gy4n

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