“…While a fully quantum description of this interaction has also been developed [17,21], probably its most revealing description has been furnished by the semiclassical model provided by the Maxwell-Bloch system of equations [17,[22][23][24][25]. This model has helped to uncover the fundamentals of the resonant interaction between an electromagnetic field and a system of active atoms in the regime in which the field can be described classically and the medium by quantum mechanics, and in which a great number of the relevant experiments have been carried out [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. In fact, many physical effects observed in these experiments, from the photon echo [2] and self-induced transparency [3,4] to the chaotic laser dynamics [11], have been explained using the MaxwellBloch equations in the idealized two-level approximation, in which the light is assumed to be monochromatic and to interact resonantly with only two active atomic levels in the optical medium [17,[23][24][25][26][27][28].…”