Editor's Summary

10 August 2006

Many ions make light work


The elementary particles of light that propagate through air are photons. But when light propagates through condensed matter, it couples to the underlying lattice, resulting in complex particles such as polaritons. A new study makes use of ultrafast X-ray diffraction to directly observe atomic displacements that support such optical excitations in a solid. In this study, terahertz radiation propagating through the ferroelectric lithium tantalate (LiTaO3) couples to lattice vibrations, resulting in phonon-polariton waves. This new X-ray diffraction technique makes it possible to follow the absolute displacements of ions in the lattice that underlie the propagation of these waves.

LetterTracking the motion of charges in a terahertz light field by femtosecond X-ray diffraction

A. Cavalleri, S. Wall, C. Simpson, E. Statz, D. W. Ward, K. A. Nelson, M. Rini & R. W. Schoenlein

doi:10.1038/nature05041