Electrons, protons and even ions can be accelerated using the extreme electric fields generated when a high-power laser is focused into a plasma. But the structure of the so-called laser wakefields that are driven through the plasma at almost the speed of light — analogous to the wake produced behind by a boat as it travels on water — has until now only been discernable through simulations of the process. Nicholas Matlis and colleagues have produced the first direct images of a laser wakefield, by using a holographic technique that reconstructs an image of the wake structures from the way in which they perturb the interference of two coherent light beams passing through the plasma. The technique provides a new tool for studying laser–plasma interactions and potentially improving the performance of laser-driven particle accelerators.
Nature Physics Published online: 2, 749 - 753 (October 2006)