Photon echo signals: Beyond unit efficiency

We have investigated the energy efficiency of optical coherent transient signals (two- and three-pulse echoes) as a function of excitation and material parameters. Simulations, numerical integrations of the coupled Maxwell-Bloch equations, reveal accessible regions of parameter space (outside those normally utilized in experimental work) wherein transient signals contain as much or more energy than one of the excitation pulses used to create them. This result conflicts with the widely held perception and experimental observation that transient signals are energetically feeble. Transients generated in the parameter ranges identified may have enhanced value in scientific and technical applications.