New compact on-chip device stops light in its tracks

It is essential to understand the oscillation of light waves while interacting with materials to know how light-driven energy transfers in materials.

This is quite a difficult task to perform as lit waves oscillated at breakneck speed. Although, scientists have yet to develop a compact device with enough time resolution to capture them directly.

Now, this task has been accomplished by MIT scientists. They have developed chip-scale devices to trace the weak electric field of light waves as they change in time. The device is equipped with a microchip that uses short laser pulses and nanoscale antennas.

This new device is expected to help scientists demonstrate new tools for optical measurements with applications in areas such as biology, medicine, food safety, gas sensing, and drug discovery.

Co-author Phillip Donnie Keathley, group leader and Research Laboratory of Electronics (RLE) research scientist, said, “The potential applications of this technology are many. For instance, researchers will better understand visual absorption pathways in plants and photovoltaics or better identify molecular signatures in complex biological systems using these optical sampling devices.”

Using short laser pulses, the microchip creates extremely fast electronic flashes at the tips of nanoscale antennas. These nanoscale antennas enhance the field of the short laser pulse to the point that they are strong enough to rip electrons out of the antenna. 

This generates an extremely brief electronic flash that is quickly deposited into a collecting electrode. And these flashes last only a few hundred attoseconds (a few one-hundred-billionths of one-billionth of 1 second).

Scientists used these flashes to take snapshots of much weaker light waves oscillating as they passed by the chip.

Professor Peter Hommelhoff, chair for laser physics at the University of Erlangen-Nuremberg, who was not connected with this work, said, “This work shows, once more, how the merger of nanofabrication and ultrafast physics can lead to exciting insights and new ultrafast measurements tools. All this is based on a deep understanding of the underlying physics. Based on this research, we can now measure ultrafast field waveforms of very weak laser pulses.”

Scientists noted, “The ability to measure light waves in time directly would benefit both science and industry. As light interacts with materials, its waves are altered in time, leaving signatures of the molecules inside. This optical field sampling technique promises to capture these signatures with greater fidelity and sensitivity than prior methods while using compact and integrable technology needed for real-world applications.”

Journal Reference:

1.  Mina R. Bionta et al. On-chip sampling of optical fields with attosecond resolution, Nature Photonics (2021). DOI: 10.1038/s41566-021-00792-0

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