Temporal Spinwave Fabry-Perot Interferometry via Coherent Population Trapping

TL;DR

This paper demonstrates a novel temporal spinwave Fabry-Perot interferometry technique using double-$\Lambda$ CPT in laser-cooled $^{87}$Rb atoms, enabling easier identification of the central Ramsey fringe and magnetic field measurement.

Contribution

The work introduces a new interferometry method based on temporal spinwaves, providing a clearer spectral signature and a magnetic field sensing application.

Findings

Transmission spectrum forms a comb of peaks due to constructive interference.

Peak splitting occurs under magnetic fields, enabling magnetic sensing.

Analytical explanation via optical Bloch equations confirms the interferometry mechanism.

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-P\'{e}rot interferometry via double-$\Lambda$ 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-$\Lambda$ system, the transmission spectrum is analytically explained by the Fabry-P\'{e}rot interferometry of temporal spinwaves. Due to small amplitude difference between the two Land\'{e} 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.