Crossover from electromagnetically induced transparency to Autler-Townes splitting in open V-type molecular systems

We investigate electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) in an open V-type molecular system. Through detailed analytical calculations of the absorption spectrum of a probe laser field using the residue theorem and spectrum decomposition, we find that EIT may occur and a crossover from EIT to ATS exists for hot molecules. However, there is no EIT and hence no EIT-ATS crossover for cold molecules. Furthermore, we prove that for hot molecules EIT is allowed even for a counter-propagating configuration. We provide explicit formulas of EIT conditions and widths of EIT transparency windows of the probe field when hot molecules work in copropagating and counter-propagating configurations, respectively. Our theoretical result agrees well with the recent experimental ones reported by Lazoudis et al. [Phys. Rev. A 83, 063419 (2011)]. DOI: 10.1103/PhysRevA.87.043813