Crossover from electromagnetically induced transparency to Autler-Townes splitting in open ladder systems with Doppler broadening

We propose a general theoretical scheme to investigate the crossover from electromagnetically induced transparency (EIT) to Autler-Townes splitting (ATS) in open ladder-type atomic and molecular systems with Doppler broadening. We show that when the wavenumber ratio kc/kp approximate to -1, EIT, ATS, and EIT-ATS crossover exist for both ladder-I and ladder-II systems, where kc (kp) is the wavenumber of control ( probe) field. Furthermore, when kc/kp is far from -1, EIT can occur, but ATS is destroyed if the upper state of the ladder-I system is a Rydberg state. In addition, ATS exists but EIT is not possible if the control field used to couple the two lower states of the ladder-II system is a microwave field. The theoretical scheme developed here can be applied to atoms, molecules, and other systems ( including Na-2 molecules, and Rydberg atoms), and the results obtained may have practical applications in optical information processing and transformation. (C) 2014 Optical Society of America