Low-light-level all-optical switching based on stored light pulses

We have experimentally and theoretically studied the scheme of all-optical switching based on stored light pulses. In the scheme, a probe pulse is stored in the medium by the effect of electromagnetically induced transparency and a switching pulse is applied during the storage in order to turn off the probe transmission in the retrieval process. Our study takes into account the attenuation of the switching pulse induced by the stored probe pulse. The consistency between the experimental data and the theoretical predictions from the numerical calculation is satisfactory. We further derive the analytical expressions of energy losses of the probe and switching pulses. The results from the analytical expressions are in good agreement with those from the numerical calculation. Using the analytical expressions, we investigated the switching efficiency with the consideration of the Gaussian beam profile of the photon pulses and explored the feasibility of switching a single photon by another.