Material mirrors are not necessarily needed to direct laser light. A research team under British leadership and with the participation of Heinrich Heine University Düsseldorf (HHU) has experimentally verified a fundamentally new concept: the reflection of light on regular plasma structures. This method could be particularly important for compact high-power lasers. The "ghost mirror" does not require classic reflective solid surfaces. Structures are briefly induced in plasmas that can also reflect or otherwise manipulate light.
The research team created a layered plasma mirror using counter-rotating laser beams. The laser beams generate a beat wave in the plasma, which in turn drives the electrons and ions in the plasma into the regular lattice structure, creating a very robust mirror with high reflectivity. However, it is very volatile and only exists for a few hundred picoseconds. However, this is sufficient to reflect the incomparably shorter high-power laser pulses, which have a length in the femtosecond range. The plasmas can withstand intensities of up to 1018 watts per square centimeter, which exceeds the damage threshold of conventional optical components by four to five orders of magnitude. As a result, the size of optical elements can be reduced by two or three orders of magnitude, so that optics - which would otherwise be one meter in size - could shrink to millimetres or centimetres.
