Light Pulses Modify Complex Trajectories

The electronic field moves in complex trajectories within a few femtoseconds as a light pulse propagates. (Source: G. Sansone)

For the first time an inter­national research team under the direction of Giuseppe Sansone at the Insti­tute of Physics at the Uni­versity of Freiburg has been able to com­pletely charac­terize the complex evo­lution of weak electric fields. Their charac­teristics such as the direction of oscil­lation, duration and inten­sity depend on the spatio­temporal evolution of their electric and magnetic fields.

Both of these vectors can run in complex trajec­tories as a light pulse propa­gates – for instance, they can move along a circle, an elliptical or describe any varia­tion thereof. The movement occurs on a timescale of several hundred atto­seconds, which is much faster than any ordinary electronic or opto­electronic device can measure. In order to observe how the electric field moves anyway, the team developed a method using an atto­second laser.

“Using this new tool we were able to produce electrons in the form of wave packets that only last a few hundred atto­seconds,” explains Sansone. During their dynamics, electrons are very sensitive to any kind of external dis­turbance. The researchers leveraged this charac­teristic to modify the electrons’ tra­jectories with weak visible light pulses.

They were then able to measure how the trajec­tories had been altered, thereby deducing the inten­sity and direc­tion of the electric field. “Our method will enable researchers in the future to have a complete charac­terization of elec­tronic dynamics in solids by measuring the visible light reflected on its surface,” says Sansone. (Source: U. Freiburg)

Reference: P. A. Carpeggiani et al.: Vectorial optical field reconstruction by attosecond spatial interferometry, Nat. Photon. 11, 383 (2017); DOI: 10.1038/nphoton.2017.73

Links: Dipartimento di Fisica (G. Sansone), Politecnico di Milano, Italy

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