Light in the nanoworld

Quantum light sources pave the way for optical circuits.

A team of international scientists led by Alexander Holleitner and Jonathan Finley, physicists at the Technical University of Munich (TUM), has successfully placed light sources within an atomically thin material layer with a precision of just a few nanometers. This new method could have a multitude of applications such as quantum technologies, from quantum sensors and transistors in smartphones through to new encryption technologies for data transmission.

Previous circuits on chips depend on electrons as the information bearers. Later on, photons which transmit data at the speed of light will be able to take this task in optical circuits. Quantum light sources, which are then associated with quantum fiber optic cables and finders are required as essential building blocks for such new chips.

Scientists have now successfully created such quantum light sources in atomically thin material layers and placing them with nanometer accuracy.

Julian Klein, a lead author of the study, said, “This constitutes a first key step towards optical quantum computers. Because for future applications the light sources must be coupled with photon circuits, waveguides, for example, to make light-based quantum calculations possible.”

Scientists used a layer of the semiconductor molybdenum disulfide (MoS2) as the starting material, which is just three atoms thick. They irradiated this with a helium ion beam which they concentrated on a surface area of less than one nanometer.

To produce optically active defects, the ideal quantum light sources, molybdenum or sulfur atoms are accurately worked out of the layer. The imperfections are traps for so-called excitons, electron-hole pairs, which at that point discharge the desired photons.

The new helium ions at the Walter Schottky Institute’s Center for Nanotechnology and Nanomaterials, which can be utilized to illuminate such material with an unparalleled lateral resolution, was of central importance for this.

Scientists later created a model to describe the energy states observed at the imperfections in theory. Scientists, in future, want to create more complex light source patterns such as in lateral two-dimensional lattice structures to research multi-exciton phenomena or exotic material properties.

The study is published in the journal Nature Communications.

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