Impurities improve the performance of nanolasers

Australian National University (ANU) scientists have improved the performance of tiny lasers by adding impurities, leading to a 100-fold improvement in the amount of light emitted from the lasers.

In a study led by PhD student Tim Burgess and published in the journal Nature Communications, atoms of zinc were added to lasers one hundredth the diameter of a human hair and made of gallium arsenide — a common material used in photovoltaic cells, lasers and LEDs.

“Normally you wouldn’t even bother looking for light from nanocrystals of gallium arsenide — we were initially adding zinc simply to improve the electrical conductivity,” said Burgess.

“It was only when I happened to check for light emission that I realised we were onto something.”

Gallium arsenide is challenging to work with at the nanoscale as the material requires a surface coating before it will produce light. Previous ANU studies have shown how to fabricate suitable coatings, while the latest study has complemented these successes by increasing the amount of light generated inside the nanostructure.

“It is an exciting discovery and opens up opportunities to study other nanostructures with enhanced light emission efficiency so that we can shrink the size of the lasers further,” said research group leader Professor Chennupati Jagadish.

Burgess noted that the addition of the impurity to gallium arsenide, a process called doping, did not only improve the light emission.

“The doped gallium arsenide has a very short carrier lifetime of only a few picoseconds, which meant it would be well suited to use in high-speed electronics components,” he said. This means it could be utilised in the development of low-cost biomedical sensors, quantum computing and a faster internet.

“The doping has really given these nanolasers a performance edge,” Burgess said.