Spectroscopy of cesium Rydberg atoms in strong radio-frequency fields

TL;DR

This study explores how strong RF fields affect cesium Rydberg atoms, revealing complex spectral phenomena and demonstrating a calibration-free optical method for RF field measurement using Rydberg-EIT spectroscopy.

Contribution

The paper provides a detailed experimental and theoretical analysis of Rydberg atom responses to strong RF fields, introducing a Floquet-based model that matches observed spectra.

Findings

Observation of RF-induced spectral sidebands and state-mixing in Rydberg atoms

Validation of Floquet analysis for modeling strong RF field effects

Demonstration of optical RF field measurement technique

Abstract

We study Rydberg atoms modulated by strong radio-frequency (RF) fields with a frequency of 70 MHz. The Rydberg atoms are prepared in a room temperature cesium cell, and their level structure is probed using electromagnetically induced transparency (EIT). As the RF field increases from the weak- into the strong-field regime, the range of observed RF-induced phenomena progresses from AC level shifts through increasingly pronounced and numerous RF-modulation sidebands to complex state-mixing and level-crossings with high-l hydrogen-like states. Weak anharmonic admixtures in the RF field generate clearly visible modifications in the Rydberg-EIT spectra. A Floquet analysis is employed to model the Rydberg spectra, and good agreement with the experimental observations is found. Our results show that all-optical spectroscopy of Rydberg atoms in vapor cells can serve as an antenna-free, atom-based and calibration-free technique to measure and map RF electric fields and to analyze their higher-harmonic contents.