Group delayed phase switching of Gaussian light pulses via a thermal atomic medium

We show group delayed phase switching of a Gaussian pulse transmitting through a thermal four-level atomic medium using relative phase of the cyclically driven one microwave and two optical fields. The present scheme explains that in the presence of the atom's dephasing reservoir, a plane-polarized probe light through the medium exhibits double electromagnetically induced transparency (EIT). Upon tuning the relative phase of the coupling fields, the double EIT converts into two asymmetric mirror inversion-like single EIT phenomenon. In parallel, we develop an input-output theory for probing Gaussian pulse through the thermal medium with a nonlinear dispersion to generate group delay (advancement) and switching of the group delay (advancement) using the relative phase of the driving fields. For collinear driving fields, the transmission of the pulses through the medium appears irrespective of the wave-vector mismatch and Doppler broadening effect. Consequently, the group delay and the group delay phase switching perform without measurable pulse distortion.