Photon/spin echo in a Fabry-Perot cavity.

The pulse area theorem is a well-known versatile analytical tool for capturing the general nonlinear nature of light propagation in a two-level medium. Here we derive the pulse area theorem for the photon/spin echo signal generated in a one-side cavity. The obtained analytical solutions for primary and secondary echo pulse areas allow us to describe the nonlinear patterns of the photon/spin echo signals in an atomic ensemble in a cavity.

Two-pulse photon echo area theorem in an optically dense medium.

We perform a theoretical and experimental study of the two-pulse photon echo area conservation law in an optically dense medium. The experimental properties of the echo signal are studied at 4K on the optical transition  H (1)→H (1) (793 nm) of Tm  in a YAG crystal for a wide range of pulse areas of the two incoming light pulses, up to 4 and ≈7 respectively, with optical depth 1.5.