Coherent response to optical excitation in a rare-earth ion doped   crystal
  We investigate coherent propagation through a large optical density Tm$^{3+}$:YAG crystal. Using an ultra-stable laser, fiber filtering and site selection, we investigate the transmitted pulse temporal profile. The plane wave condition is satisfied by selection of the illuminated spot central area. We pay special attention to $\pi$-pulse transmission in the prospect of implementing optical quantum storage protocols. 
J. Ruggiero, T. Chaneli\`ere, J.-L. Le Gou\"et