Realistic theory of electromagnetically-induced transparency and slow light in a hot vapor of atoms undergoing collisions

TL;DR

This paper develops a realistic theoretical model for electromagnetically-induced transparency and slow light in hot atomic vapors, incorporating collisional effects and matching experimental results.

Contribution

It introduces a comprehensive model including velocity-changing collisions and steady-state density matrix calculations for hot atomic vapors.

Findings

Model accurately predicts EIT and slow light in hot vapors.

Collisional effects are shown to influence optical pumping and coherence.

Theoretical results agree with experimental data for helium-4 vapors.

Abstract

We present a realistic theoretical treatment of a three-level $\Lambda$ system in a hot atomic vapor interacting with a coupling and a probe field of arbitrary strengths, leading to electromagnetically-induced transparency and slow light under the two-photon resonance condition. We take into account all the relevant decoherence processes including col5Blisions. Velocity-changing collisions (VCCs) are modeled in the strong collision limit effectively, which helps in achieving optical pumping by the coupling beam across the entire Doppler profile. The steady-state expressions for the atomic density-matrix elements are numerically evaluated to yield the experimentally measured response characteristics. The predictions, taking into account a dynamic rate of influx of atoms in the two lower levels of the $\Lambda$, are in excellent agreement with the reported experimental results for $^4$He*. The role played by the VCC parameter is seen to be distinct from that by the transit time or Raman coherence decay rate.