Saturated absorption and electromagnetically induced transparency of residual rubidium in dense cesium vapor

TL;DR

This study demonstrates that residual rubidium atoms in dense cesium vapor cells exhibit saturated absorption and EIT, with the surrounding cesium acting as a buffer, enabling advanced spectroscopic and nonlinear-optical applications.

Contribution

It reveals the optical behavior of trace rubidium in dense cesium vapor and introduces a high-temperature sapphire cell for enhanced spectroscopic studies.

Findings

Residual rubidium (~1%) shows saturated absorption and EIT in cesium vapor.

Cesium acts as a buffer, improving EIT signals by reducing atomic velocity.

Cs-Rb collisional cross sections are estimated from spectra.

Abstract

In the sealed-off cesium vapor cell studied in this work, a residual rubidium fraction of approximately $\sim$1\% was observed. We investigate the optical response of these trace Rb atoms in a sealed 1~cm long Cs-filled vapor cell. Despite the low concentration, laser excitation at 795~nm allows the observation of saturated absorption and electromagnetically induced transparency (EIT) resonances. The surrounding Cs vapor effectively acts as a buffer medium, reducing the Rb atomic velocity and increasing the interaction time with the laser field, which improves the EIT signal. The experiments are performed in an all-sapphire cell that can be heated up to 500$^{\circ}$C without window blackening, unlike conventional glass cells. From the measured spectra, Cs--Rb collisional cross sections are estimated. These results show that residual atomic species in high-temperature vapor cells can be exploited for spectroscopic and nonlinear-optical studies.