H. Steudel et Dj. Kaup, Inverse scattering method applied to degenerate two-photon propagation in the low-excitation limit, J PHYS A, 33(7), 2000, pp. 1445-1457
The propagation of an optical pulse in a two-photon absorber is studied und
er the conditions that the initial pulse is detuned from exact resonance, a
nd the population of the upper level remains small. The problem is solved b
y use of a recently developed variant of the inverse scattering technique o
n a finite interval.