t the point where two ultrashort laser pulses cross, physicists can now make light oscillate through all three dimensions of space. That unusual geometry matters because some electronic quantum states have remained out of reach in experiments, even when theory said they should exist. By shaping and overlapping laser pulses from different directions, researchers at the University of Oldenburg in Germany have now created those three-dimensional light fields and used them to reach previously inaccessible states of electrons.
To build the fields, the team shaped two femtosecond laser pulses, each lasting only a few millionths of a billionth of a second, and sent them toward the same point from different directions. The beams also carried different colors of light. Where they intersected, their electric fields combined into a three-dimensional structure whose shape the researchers could control.
“The fields oscillate in all three spatial directions, opening up new possibilities for investigating and controlling specific light-matter interactions,” explains Darius Köhnke, one of the two lead authors of the study and a PhD student in the Ultrafast Coherent Dynamics research group.
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