An international team of researchers succeeds in generating
flashes of extreme ultraviolet radiation via the reflection from a mirror that
moves close to the speed of light.
A dense sheet of electrons accelerated to close to the speed
of light can act as a tuneable mirror that can generate bursts of laser-like
radiation in the short wavelength range via reflection. A team of physicists
from the Max-Planck-Institute of Quantum Optics (MPQ) in Garching, the
Ludwig-Maximilians-Universität (LMU) München, the Queens University Belfast
(QUB) and the Rutherford Appleton Laboratory (RAL) near Oxford created such a
mirror in a recent experiment. The scientists used an intense laser pulse to
accelerate a dense sheet of electrons from a nanometre-thin foil to close to
the speed of light and reflected a counter-propagating laser pulse from this
relativistic mirror. With this experiment, the physicists managed to carry out
a Gedankenexperiment (thought experiment) formulated in 1905 by Albert Einstein
stating that the reflection from a mirror moving close to the speed of light
could in principle result in bright light pulses in the short wavelength range.
The researchers report on their results in Nature Communications, 23. April,
2013.