Inevitable Imperfection Produces Nanolaser

Nanostructures are imperfect, so it has been impossible thus far to develop optical chips that can control light. But now such imperfection is now proving perfect for a whole new set of uses.

A team from the Niels Bohr Institute at the University of Copenhagen and from Technical University of Denmark took advantage of imperfect optical chips to create a nanolaser: a controllable, compact, energy-efficient light source.

Researchers are working to create as perfect a regular structure of holes as possible to control light in certain optical circuits. Images courtesy of Nature Nanotechnology.

The researchers created a structure of holes (which are themselves irregular) to control light in certain optical circuits, etching a pattern at a distance of 380 nm into clear gallium arsenide photonic crystal membranes about 25 µm in width and about 340 nm thick.

“It turns out that the imperfect optical chips are extremely well-suited for capturing light,” said Peter Lodahl, professor and head of the quantum photonic research group at Niels Bohr. “When the light is sent into the imperfect chip, it will hit the many small irregular holes, which reflect the light in random directions.” The frequent reflections cause the spontaneous capture of the light, which cannot escape. The light is then amplified, “resulting in surprisingly good conditions for creating highly efficient and compact lasers,” he added.

The imperfect nature of crystal membrane holes causes light to go back and forth, turning it into laser light on a nanometer scale.

The light source is integrated into the photonic crystal itself, consisting of a layer of artificial atoms that emit light. The photons are sent through the crystal membranes and, upon hitting the holes, the light is reflected and channeled into a waveguide. The imperfect nature of these holes causes the light to be thrown back and forth, intensifying it and turning it into laser light on a nanometer scale.

“The fact that we can control the light and produce laser light on a nanometer scale can be used to create circuits based on photons instead of electrons, thus paving the way for optical quantum communication technology in the future,” Lodahl said. “With built-in laser sources, we will be able to integrate optical components, and it allows for the building of complex functionalities.”

The researchers’ goal is to build a quantum Internet in which coded information exists in individual photons.

The research is published in Nature Nanotechnology.

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