Steered Light Could Replace Lasers for Military, Commercial Applications.

• Author: Tegler, Jan

Sandia National Laboratories recently made a breakthrough that could lay the groundwork for replacing power-hungry laser beams with ordinary light.

Two lab research scientists, Igal Brener and Prasad Iyer, proved it's possible to steer light from conventional sources like light bulbs or flashlights.

"We've shown a proof of principle that incoherent light emissions can be dynamically steered," Iyer explained.

The technology could be used in applications ranging from remote sensing and holographic displays to high-speed communications.

Incoherent light is the diffused or scattered light produced by familiar devices such as incandescent and LED bulbs. Coherent light is the focused light produced by lasers. Until last November, experts in nanophotonics and ultra-fast optics considered it impossible to dynamically steer incoherent light.

Brener and Iyer achieved the breakthrough by embedding light emitters called quantum dots in artificially structured material known as a "metasurface" on a reflective mirror.

Quantum dots have been known of in the semiconductor field for decades, Brener said. "It's only now that they are being applied practically. For example, you have quantum dot screens for TVs. There are companies now making micro-LED displays that utilize a different type of quantum dot."

Iyer described the metasurface as an extremely thin optical element which recreates the refractive properties--the ability to bend and focus light--of the curved lenses found in cameras or the human eye in a "flat nanostructure at submicron thickness."

Comprising meta-atoms

--the miniscule components semiconductors are made from --metasurfaces are capable of reflecting light with amazing efficiency. Research using metasurfaces to help steer light rays has been undertaken before but presented a challenge because these artificial structures had only been designed for coherent light sources.

Working in the Center for Integrated Nanotechnologies facility at Los Alamos National Laboratory, the researchers paired the metasurface, quantum dots and reflective mirror with a spatial light modulator.

The modulator "structured an optical pulse generated separately," according to Iyer, and projected it onto the metasurface to change the way the surface reflected light by dynamically steering the ultra-fast quantum dot emissions. Brener and Iyer found that the light waves could be focused and steered over a 70-degree range for about a trillionth of a second --long enough...