Discriminating electromagnetically induced transparency from Autler–Townes splitting in a Ξ system

Abstract

In this work, we report on experimentally discerning Autler–Townes splitting (ATS) from electromagnetically induced transparency (EIT). Our findings are based on a Ξ (ladder) transition 5S1/2→5P3/2→5D5/2 of 87Rb atoms under different laser detuning combinations. Based on the ratio of power levels of two individual and counter-propagating lasers through a room temperature Rb vapor cell, we experiment on two different categories of Ξ configuration: types I and II. For type I, 5P3/2→5D5/2 transition is strongly driven, and we observe EIT. Type II (5S1/2→5P3/2 strongly coupled) exhibits pure ATS. Under two different two-photon detuning conditions, ATS and EIT are studied. While ATS becomes stronger near exact two-photon resonance condition, the EIT weakens. This is supported by the analysis of blue light emanating from 5D5/2→6P3/2→5S1/2 decay. The complete opposite behavior of these two phenomena at exact two-photon resonance condition can be used to clearly discern EIT from ATS.