A Quantum Leap in Light Research
Physicists have managed to capture the behavior of extremely short laser pulses during focusing by means of very high spatial and temporal resolution. The results are of fundamental relevance to understanding the interactions between light and matter and will make it possible to control electron movements and chemical reactions to an extent that was previously not feasible. These insights into fundamental physics will particularly profit further research into new radiation sources and in the field of light wave electronics.
Ultrashort light pulses with such a wide optical spectrum range that the beams appear white are in common use nowadays. In almost all these applications, the white laser pulses need to be focused. As it is the specific form of the light wave that determines how electrons, for example, will move within it, it is essential to know what the focused laser beam actually looks like in detail.
It is important for researchers to know how and where the maximum of a light wave will strike electrons in an experiment or application in order to have a targeted influence on them. The changes to and propagation of light waves in an electrical field take place on a time scale of a few hundred attoseconds. Until recently, it was not possible to measure the exact distribution of the wave troughs and peaks at the focus of a laser beam on this time scale.
Researchers in Erlangen and Jena have now achieved this by focusing laser pulses onto a nanometer-sharp metal tip, causing the tip to emit electrons. These electrons act as a kind of sensor that enables the researchers to interpret the exact form of the light wave.
Original Pulication: D. Hoff, M.l Krüger, L. Maisenbacher, A. M. Sayler, G. G. Paulus & P. Hommelhoff; “Tracing the phase of focused broadband laser pulses”, Nature Physics’; doi:10.1038/nphys4185