Dynamic transition from complete population transfer to self-induced transparency

Abstract

We explore the connection between adiabatic rapid passage, a technique that allows for robust complete population transfer (CPT) in a resonant absorber, and self-induced transparency solitons. We employ the auxiliary differential equation finite-difference time-domain method to fully resolve the dynamics of femtosecond light pulses propagating through an absorbing two-level medium. Using the example of linearly chirped Gaussian pulses we find that the pulses achieving robust CPT for a single two-level system are also pulses that will transform into solitary waves when incident on a resonantly absorbing medium. At the entrance into the absorber strongly chirped, adiabatic pulses completely transfer the electronic population from the ground to the upper state. As the pulses suffer absorption they undergo a dynamic transition and quickly split into an off-resonant radiation part and one or several unchirped solitary pulses that may carry away some of the initially achieved population inversion. This spectral and temporal transformation process limits the spatial depths of the region of CPT in a dense absorber regardless of the initial pulse amplitude. We also show that the frequency-domain pulse area, defined as the spectral amplitude at the resonance frequency, allows for a better distinction between the regimes of $2\ensuremath{\pi}$-pulse and $0\ensuremath{\pi}$-pulse formation than time-domain measurements.