Abstract
The interaction of two incident laser pulses with a dielectric medium composed of three-level atoms is discussed. Particular attention is paid to various effects connected with the well known dark state or trapping state of lambda systems. Strong- and weak-field adiabatic processes are considered, taking note of the two-photon adiabatic criterion and counter-intuitive pulse sequencing. Results include two-photon absorption formulae two-photon soliton solutions, and graphs showing the propagation of the recently discovered two-photon trapping states of the field.