Bragg microcavities created by the collision of half-cycle Gaussian and rectangular attosecond light pulses in a time-dependent resonant medium

This paper examines the behavior of dynamic microcavities (DM) in multi-level resonant media when attosecond unipolar pulses of different shapes (Gaussian and rectangular) collide, acting as 2π-like selfinduced transparency pulses. In the case of realistic quasi-unipolar pulses, the influence of the opposite polarity trailing edge is investigated, and conditions under which the trailing edge’s effect can be ignored are found analytically and then confirmed by a direct numerical calculation. We demonstrate that the collision of sub-cycle pulses in a medium results in a rapid change of the refractive index both in time and space. Thus, the resonant medium under the action of a sequence of pulses considered here is an example of a time-dependent medium. The findings demonstrate the feasibility of creating time-dependent media in an atomic medium with high polarization relaxation times T2, and subsequently controlling them with half-cycle pulses at an extremely short timescale of half of an electromagnetic field oscillation.