Equations with partial derivatives and differential equations used for simulating acausal pulses

Some phenomena in physics (photonic echo) appears for an external observer as non-causal pulses suddenly emerging from an active medium (prepared by some other optical pulses) being hard to be simulated. It is shown that such functions can be put in correspondence with acausal pulses in physics (generated by the wave-equation considered on the length interval (0, 1) (an open set), starting at the initial moment of time from null initial conditions). Consequences for a possible control of such phenomena are also presented.