Continuous-probe solutions for self-similar pulses in four-level systems

We propose the use of a copropagating probe pulse in experimental tests of correlated pulse theory. We present formulas for amplitudes and velocities of a self-similar pulse trio propagating in a medium with energy levels in the configuration of the letter N. Remarkably, in contrast to previous theoretical studies, we find that the inclusion of the probe pulse lifts a rigid restriction on the oscillator strengths of the transitions.