Scientists in Germany combine spectroscopic techniques to vastly improve spatial and temporal resolution

Scientists combining light pulses with traditional microscopy have demonstrated how it is possible to capture vastly clearer images of the quantum world.

The demonstration of “light-wave electronics” at atomic scale, by two European-based researchers, is described as “unprecedented” by a leading U.S.-based quantum engineer.

Director, Klaus Kern, and scientist, Manish Garg, of the Max Planck Institute for Solid State Research in Stuttgart, Germany, jointly published their research on attosecond manipulation of electrons. Their research combines laser pulses with microscopy to essentially shoot “slow-motion movies” at high resolution. Attosecond manipulation aims to deliver clear and direct information about the core of atoms, molecules, nanostructures and solids. A future possibility is to control these fundamental processes of matter with attosecond manipulation.

“By irradiating the tunnel junction with carrier-enveloped, phase-stabilized femtosecond light pulses, Garg and Kern effectively combined the two methods to demonstrate a technique capable of both high-temporal and high-spatial resolution of the elementary processes in matter,” according to a summary of Nanophotonics published by Ian S. Osborne.

Spectroscopy allows for excellent temporal [time] resolution while microscopy allows for excellent spatial resolution. Clarice Aiello, a quantum engineer at the Quantum Biology Tech (QuBiT) Lab at the University of California, Los Angeles (UCLA), in a piece published by Science magazine said that achieving both at the same time is harder to do.

Aiello's interests include using quantum physics to inform biology at nanoscale levels.

“The ultimate goal of any nanotechnology is to resolve and control elementary processes in matter,” she wrote. “In general, although many spectroscopies can achieve high temporal resolution and many microscopies can achieve high spatial resolution, achieving both is difficult. Garg and Kern improve the limits of concomitant spatial and temporal resolutions by combining scanning tunneling microscopy [STM] with an ingenious phase-locking train of ultrafast optical pulses.

“The authors go on to demonstrate that their instrument can deconvolute femtosecond electron dynamics with nanoscale resolution,” Aiello continued. “These feats are only made more interesting because the phase-locking scheme enables an imprint of the laser's [coherent] phase onto the tunneling electrons. This demonstration of 'light-wave electronics' at atomic scales is unprecedented.”

Devices operating in the quantum world need proper manipulation and control over electrons at atomic length and time scales, the authors stated.

“We demonstrate coherent control over electrons in a tunnel junction of a scanning tunneling microscope by means of precise tuning of the carrier-envelope phase of two-cycle long [<6-femtosecond] optical pulses,” they wrote. “We explore photon and field-driven tunneling, two different regimes of interaction of optical pulses with the tunnel junction, and demonstrate a transition from one regime to the other.

“Our results show that it is possible to induce, track and control electronic current at atomic scales with sub-femtosecond resolution, providing a route to develop petahertz-coherent nanoelectronics and microscopy.”