Formation of strongly shifted EIT resonances using "forbidden" transitions of Cesium

TL;DR

This paper demonstrates the formation of strongly shifted EIT resonances in Cesium using magnetically induced forbidden transitions in strong magnetic fields, with potential applications in precision spectroscopy.

Contribution

First experimental use of magnetically induced forbidden transitions of Cesium to generate shifted EIT resonances in strong magnetic fields using a nanometric cell.

Findings

Achieved a 12 GHz frequency shift of EIT resonances at 3 kG magnetic field.

Observed large frequency shift slope of ~4 MHz/G for MI transitions.

Experimental results agree with Doppler-broadened three-level system calculations.

Abstract

Atomic transitions satisfying $F_e - F_g = \Delta F = \pm 2$ (where $F_e$ stands for excited and $F_g$ stands for ground state) of alkali atoms have zero probability in zero magnetic field (they are so-called "forbidden" transitions) but experience a large probabilty increase in an external magnetic field. These transitions are called magnetically induced (MI) transitions. In this paper, we use for the first time the $\sigma^+$ ($\Delta m_F~=~+1$) MI transitions $F_g = 3 \rightarrow F_e = 5$ of {Cesium} as probe radiation to form EIT resonances in strong magnetic fields (1 - 3 kG) while the coupling radiation frequency is resonant with $F_g=4\rightarrow F_e=5$ $\sigma^+$ transitions. The experiment is performed using a nanometric-thin cell filled with Cs vapor and a strong permanent magnet. The thickness of the vapor column is 852 nm, corresponding to the Cs $D_2$ line transition wavelength. Due to the large frequency shift slope of the MI transitions ($\sim$ 4 MHz/G), it is possible to form contrasted and strongly frequency-shifted EIT resonances. Particularly, a strong 12 GHz frequency shift is observed when applying an external magnetic field of $\sim$ 3 kG. Preliminary calculations performed considering Doppler-broadened three level systems in a nanocell are in reasonable agreement with the experimental measurements.