Experimental observation of photon echoes and power-efficiency analysis in a cavity environment

We present what is, to our best knowledge, the first experimental demonstration of echo signals generated from a sample in an optical cavity. The configuration allows us to use an optically thin sample and still have high effective absorption as well as relatively uniform excitation in the longitudinal direction within the sample. We observed echo signal power of up to twice that of certain input fields. The observed efficiency is much greater than the normally expected few percent. By using an input field encoded with a bit sequence, we also show that the cavity does not introduce significant distortion into the reproduced signal.