Nanostructures enable record high-harmonic generation

Date:
July 21, 2021
Source:
Cornell University
Summary:
Researchers have developed nanostructures that enable
record-breaking conversion of laser pulses into high-harmonic
generation, paving the way for new scientific tools for
high-resolution imaging.



FULL STORY ========================================================================== Cornell researchers have developed nanostructures that enable
record-breaking conversion of laser pulses into high-harmonic generation, paving the way for new scientific tools for high-resolution imaging and studying physical processes that occur at the scale of an attosecond --
one quintillionth of a second.


========================================================================== High-harmonic generation has long been used to merge photons from a
pulsing laser into one, ultrashort photon with much higher energy,
producing extreme ultraviolet light and X-rays used for a variety of
scientific purposes.

Traditionally, gases have been used as sources of harmonics, but
a research team led by Gennady Shvets, professor of applied and
engineering physics in the College of Engineering, has shown that
engineered nanostructures have a bright future for this application.

The research is detailed in the paper "Generation of Even and Odd High Harmonics in Resonant Metasurfaces Using Single and Multiple Ultra-Intense Laser Pulses," published July 7 in Nature Communications. Maxim
Shcherbakov, who conducted the research as a Cornell postdoctoral
associate before becoming an assistant professor at the University of California, Irvine, is the lead author.

The nanostructures created by the team make up an ultrathin resonant
gallium- phosphide metasurface that overcomes many of the usual problems associated with high-harmonic generation in gases and other solids. The gallium-phosphide material permits harmonics of all orders without
reabsorbing them, and the specialized structure can interact with the
laser pulse's entire light spectrum.

"Achieving this required engineering of the metasurface's structure using
full- wave simulations," Shcherbakov said. "We carefully selected the parameters of the gallium-phosphide particles to fulfill this condition,
and then it took a custom nanofabrication flow to bring it to light."
The result is nanostructures capable of generating both even and odd
harmonics -- a limitation of most other harmonic materials -- covering
a wide range of photon energies between 1.3 and 3 electron volts. The record-breaking conversion efficiency enables scientists to observe
molecular and electronic dynamics within a material with just one laser
shot, helping to preserve samples that may otherwise be degraded by
multiple high-powered shots.

The study is the first to observe high-harmonic generated radiation from a single laser pulse, which allowed the metasurface to withstand high powers
- - five to 10 times higher than previously shown in other metasurfaces.

"It opens up new opportunities to study matter at ultrahigh fields,
a regime not readily accessible before," Shcherbakov said. "With our
method, we envision that people can study materials beyond metasurfaces, including but not limited to crystals, 2D materials, single atoms,
artificial atomic lattices and other quantum systems." Now that the
research team has demonstrated the advantages of using nanostructures
for high-harmonic generation, it hopes to improve high-harmonic devices
and facilities by stacking the nanostructures together to replace a
solid-state source, such as crystals.

Co-authors include Cornell postdoctoral researchers Zhiyuan Fan and
Giovanni Sartorello, and researchers from the Ohio State University and
the Institute of Materials Research and Engineering in Singapore.

The research was funded by the Office of Naval Research, the Cornell
Center for Materials Research through the National Science Foundation's Materials Research Science and Engineering Centers program, and the Air
Force Office of Scientific Research.

========================================================================== Story Source: Materials provided by Cornell_University. Original written
by Syl Kacapyr.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Maxim R. Shcherbakov, Haizhong Zhang, Michael Tripepi, Giovanni
Sartorello, Noah Talisa, Abdallah AlShafey, Zhiyuan Fan,
Justin Twardowski, Leonid A. Krivitsky, Arseniy I. Kuznetsov,
Enam Chowdhury, Gennady Shvets. Generation of even and odd high
harmonics in resonant metasurfaces using single and multiple
ultra-intense laser pulses. Nature Communications, 2021; 12 (1)
DOI: 10.1038/s41467-021-24450-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210721120717.htm

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