Continuous reversal of Hanle resonances of a counter-propagating pulse and continuous-wave field

In this work we study propagation dynamics of two counter-propagating lasers, a continuous-wave (CW) laser and the pulse of another laser, when both lasers are tuned to the F_g = 2 → F_e = 1 transition in ⁸⁷Rb, and can therefore develop Hanle electromagnetically induced transparency (EIT) in Rb vapor. We calculate the transmission of both lasers as a function of applied magnetic field, and investigate how the propagation of the pulse affects the transmission of the CW laser. Vice versa, we have found conditions when the Gaussian pulse can either pass unchanged, or be significantly absorbed in the vacuum Rb cell. This configuration is therefore suitable for convenient control of the pulse propagation and the system is of interest for optically switching the laser pulses. In terms of the corresponding shapes of the coherent Hanle resonances, this is equivalent to turning the coherent resonance from Hanle EIT into an electromagnetically induced absorption (EIA) peak. There is a range of intensities of both the CW laser and the laser pulse when strong drives of atomic coherences allow the two lasers to interact with each other through atomic coherence and can simultaneously reverse the signs of the Hanle resonances of both. (paper)