Ultrafast beam-steering breakthrough

Date:
March 20, 2023
Source:
DOE/Sandia National Laboratories
Summary:
n a major breakthrough in the fields of nanophotonics and ultrafast
optics, a research team has demonstrated the ability to dynamically
steer light pulses from conventional, so-called incoherent light
sources.


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FULL STORY ==========================================================================
In a major breakthrough in the fields of nanophotonics and ultrafast
optics, a Sandia National Laboratories research team has demonstrated the ability to dynamically steer light pulses from conventional, so-called incoherent light sources.


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This ability to control light using a semiconductor device could allow
low- power, relatively inexpensive sources like LEDs or flashlight
bulbs to replace more powerful laser beams in new technologies such as holograms, remote sensing, self-driving cars and high-speed communication.

"What we've done is show that steering a beam of incoherent light can
be done," said Prasad Iyer, Sandia scientist and lead author of the
research, which was reported in the current issue of the journal Nature Photonics. The work was funded by the Department of Energy's Office
of Science.

Incoherent light is emitted by many common sources, such as an
old-fashioned incandescent light bulb or an LED bulb. This light is called incoherent since the photons are emitted with different wavelengths
and in a random fashion. A beam of light from a laser, however, does
not spread and diffuse because the photons have the same frequency and
phase and is thus called coherent light.

In the team's research, they manipulated incoherent light by using
artificially structured materials called metasurfaces, made from
tiny building blocks of semiconductors called meta-atoms that can be
designed to reflect light very efficiently. Although metasurfaces had previously shown promise for creating devices that could steer light
rays to arbitrary angles, they also presented a challenge because they
had only been designed for coherent light sources.

Ideally, one would want a semiconductor device that can emit light like
an LED, steer the light emission to a set angle by applying a control
voltage and shift the steering angle at the fastest speed possible.

The researchers started with a semiconductor metasurface that had embedded
tiny light sources called quantum dots. By using a control optical pulse,
they were able to change, or reconfigure, the way the surface reflected
light and steer the light waves emitted from the quantum dots in different directions over a 70-degree range for less than a trillionth-of-a-second, marking a significant success. Similar to laser-based steering, the
steered beam restrained the tendency of incoherent light to spread over
a wider viewing angle and instead produced bright light at a distance.

Taming light A feat previously considered impossible, the team's proof-of-principle work paves the way for developments in the fields of nanophotonics and ultrafast optics. The ability to dynamically control incoherent light sources and manipulate their properties offers a wide
range of applications.

One low-power use would be to brighten military helmet screens used
to overlay maps or blueprints over ordinary vision. "In applications
where space is valuable," Iyer said, "steering light emission with low-size-and-weight metasurface-LED displays could be made possible in
the future with this technology. We can use the light emitted in a better
way rather than just turning them off and on." The technique could
also provide a new kind of small display that can project holographic
images onto eyeballs using low-power LEDs, a capability of particular
interest for augmented and virtual reality devices. Other uses could be
in self-driving cars where LIDAR is used to sense objects in the path
of the car.

In terms of expressions of interest, the team has had several inquiries
from commercial sources, said Sandia researcher Igal Brener, a paper
author and lead scientist on the project. "A commercial product could
be 5-10 years out, especially if we want to have all the functionality on-chip," Brener said. "You wouldn't use a control optical pulse to
impart the changes in the metasurface needed to steer the light, but
rather you would do this control electrically.

We have ideas and plans, but it's still early. Imagine an LED light
bulb that can emit light to follow you. Then you wouldn't waste all that illumination where there's nobody. This is one of the many applications
that we dreamed about with DOE years ago for energy efficiency for
office lighting, for example." Similarly, tamed light may one day offer benefits in scenarios where focused illumination is only needed in a
specific area of interest, such as surgery or in autonomous vehicles.

For incoherent light, the future is looking bright.

Sandia National Laboratories is a multimission laboratory operated by
National Technology and Engineering Solutions of Sandia LLC, a wholly
owned subsidiary of Honeywell International Inc., for the U.S. Department
of Energy's National Nuclear Security Administration. Sandia Labs
has major research and development responsibilities in nuclear
deterrence, global security, defense, energy technologies and economic competitiveness, with main facilities in Albuquerque, New Mexico, and Livermore, California.

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========================================================================== Story Source: Materials provided by
DOE/Sandia_National_Laboratories. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Iyer, P.P., Karl, N., Addamane, S. et al. Sub-picosecond steering of
ultrafast incoherent emission from semiconductor metasurfaces. Nat.

Photon., 2023 DOI: 10.1038/s41566-023-01172-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230320143821.htm

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