Hyperfine structure and collisions in three-photon Rydberg electromagnetically induced transparency

TL;DR

This paper investigates hyperfine structure and collision effects in three-photon Rydberg EIT in rubidium vapor, revealing complex spectral patterns and the influence of argon collisions, with implications for quantum sensing technologies.

Contribution

It provides the first detailed analysis of hyperfine and collision effects in three-photon Rydberg EIT, supported by experimental spectra and 10-level simulations.

Findings

Hyperfine structure causes complex EIT spectral patterns.

Argon collisions induce an additional EIT mode.

Simulations successfully explain observed spectral features.

Abstract

Multi-photon electromagnetically-induced transparency (EIT) of atomic vapors involves several intermediate atomic levels. The sub-structure of these levels and their collisional interactions can drastically alter experimental EIT signals. Here, we report on hyperfine structure and collision effects in three-photon Rydberg EIT on the cascade $5S_{1/2} \rightarrow$ $5P_{1/2} \rightarrow 5D_{3/2}$ $\rightarrow 25F_{5/2}$ in a room temperature $^{85}$Rb vapor cell. In our measurements of EIT spectra, we identify two types of EIT signatures that correspond with distinct excitation pathways and atomic velocity classes in the atomic vapor. The $5D_{3/2}$ hyperfine structure and Autler-Townes splittings lead to complex patterns in the EIT spectra, which we analyze with the aid of 10-level EIT simulations. Adding 50~mTorr of Ar gas alters the EIT spectra and induces an additional, third EIT mode. Based on our simulation results, we attribute these changes to hyperfine collisions in the Rb $5D_{3/2}$ level. Our study may become useful in quantum technologies involving Rydberg EIT and hyperfine collisions in vapor cells, including non-invasive spatio-temporally resolved electric-field sensing of electric fields in low-pressure plasmas.