Dynamic structures created by asymmetric collisions of half-cycle attosecond pulses in a time-varying resonant medium

Half-cycle attosecond pulses formed from an electromagnetic field half-wave have the shortest duration in a given spectral interval. When these pulses interact coherently with the medium, new types of spatial structures of population inversion may emerge on each resonant transition. Based on numerical calculations, we examine the possibility of ultrafast control of these structures, such as microcavities, in an asymmetric collision of half-cycle pulses in a medium. We demonstrate that it is possible to create dynamic microcavities with controlled parameters, as well as divide the medium into different regions of near-constant population inversion. The selectivity effect is observed, with deeper structures formed on one transition than another, highlighting the possibility of fine-tuning these processes. The results show that time-dependent media could be realized in a conventional resonant medium with discrete energy levels using half-cycle pulses.