Realisation of Transparency below the One-Photon Absorption Level for a Coupling Laser Driving a Lambda System under EIT Conditions

The concept of parametric spectra in electromagnetically induced transparency is clarified. In this context, the possibility for a coupling laser to reach absorption levels below the one-photon absorption is experimentally shown. In this sense, the first results of electromagnetically induced transparency for a coupling laser in a coherent-population-trapping dominated system are presented