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arXiv:2008.12562

Temporal Spinwave Fabry-Perot Interferometry via Coherent Population Trapping

Ruihuan Fang, Chengyin Han, Xunda Jiang, Yuxiang Qiu, Yuanyuan Guo, Minhua Zhao, Jiahao Huang, Bo Lü, Chaohong Lee

Published Aug 28, 2020• 1 citation
arXivHTMLPDF

Abstract

Ramsey spectroscopy via coherent population trapping (CPT) is essential in precision measurements. The conventional CPT-Ramsey fringes contain numbers of almost identical oscillations and so that it is difficult to identify the central fringe. Here, we experimentally demonstrate a temporal spinwave Fabry-Pérot interferometry via double-$Λ$ CPT of laser-cooled $^{87}$Rb atoms. Due to the constructive interference of temporal spinwaves, the transmission spectrum appears as a comb of equidistant peaks in frequency domain and thus the central Ramsey fringe can be easily identified. From the optical Bloch equations for our five-level double-$Λ$ system, the transmission spectrum is analytically explained by the Fabry-Pérot interferometry of temporal spinwaves. Due to small amplitude difference between the two Landé factors, each peak splits into two when the external magnetic field is not too weak. This peak splitting can be employed to measure an unknown magnetic field without involving magneto-sensitive transitions.

DOI
10.48550/arxiv.2008.12562

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We demonstrate an experimental observation of coherent population trapping-Ramsey interference in cold 87 Rb atoms by employing the time-domain separated oscillatory fields' method. The interference fringe with line width of 80Hz is obtained. We propose a novel method to measure the cold atom number. The measurement is insensitive to the pump beam intensity, the single photon detuning and even the initial state population. We use this method to normalize the interference signal and to improve the signal-to-noise ratio significantly.