Physical Review LettersObservation of a Photon EchoNorman A. Kurnit, Isaac D. Abella, Sven R. HartmannPublished Nov 9, 1964• 753 citationsPublisherAbstractReceived 2 September 1964DOI:https://doi.org/10.1103/PhysRevLett.13.567©1964 American Physical SocietyDOI10.1103/physrevlett.13.567