Role of population transfer under strong probe conditions in electromagnetically induced transparency

TL;DR

This paper theoretically investigates electromagnetically induced transparency (EIT) under strong probe conditions across three- and four-level atomic systems, revealing how population transfer influences EIT features in open and closed configurations.

Contribution

It provides new insights into EIT behavior under strong probe conditions, especially the effects of population transfer in open versus closed systems and the emergence of EITA.

Findings

EIT dip nearly disappears in closed three-level systems.

EIT dip persists in open three-level systems.

A narrow EITA peak appears in four-level systems, useful for optical clocks.

Abstract

We analyze theoretically the phenomenon of electromagnetically induced transparency (EIT) under conditions where the probe laser is not in the usual weak limit. We consider the effects in both three-level and four-level systems, which are either closed or open (due to losses to an external metastable level). We find that the EIT dip almost disappears in a closed three-level system but survives in an open system. In four-level systems, there is a narrow enhanced-absorption peak (EITA) at line center, which has applications as an optical clock. The peak converts to an EIT dip in a closed system, but again survives in an open system.