Bragg microcavities created by the collision of unipolar Gaussian and rectangular attosecond light pulses in a time-varying resonant medium

This paper investigates analytically and numerically the behavior of dynamic microcavities in multi-level resonant media. They arise when attosecond unipolar pulses of different time shapes - Gaussian and rectangular - collide in the medium. These pulses act like 2π-like self-induced transparency pulses. The influence of the trailing edge of opposite polarity is studied. Conditions under which the effect of the trailing edge can be neglected are found analytically. These conditions are then confirmed by a direct numerical calculation. The use of pulses of different time shapes, as opposed to the case previously studied by the authors where pulses of the same time shape collide, opens up wider possibilities for controlling the shape of induced microcavities.