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 (DMs) in multi-level resonant media when attosecond unipolar pulses of different shapes (Gaussian and rectangular) collide, acting as 2 π -like self-induced transparency pulses. For realistic quasi-unipolar pulses, the influence of the trailing edge of opposite polarity 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 case considered here of a resonant medium under the action of a sequence of pulses 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 T 2 , and subsequently controlling them with half-cycle pulses at an extremely short timescale of half of an electromagnetic field oscillation.