Happy accident makes nanolasers shine Thursday, 28 July 2016

A young materials engineering graduate at the Australian National University (ANU) has accidentally discovered a way of improving the performance of tiny lasers by adding impurities, with novel applications, including a faster internet.

Tim Burgess, PhD candidate at the ANU Research School of Physics and Engineering, said that he added atoms of zinc to lasers one hundredth the diameter of a human hair and made of gallium arsenide, leading to a 100 times improvement in the amount of light from the lasers.

“My project was to investigate how we could add impurities to nanowires in a process known as ‘doping’,” Mr Burgess said. “After finishing some other experiments early one day, I decided to fill time by checking the light output from some doped nanowires I happened to have with me…I really wasn’t expecting much as the gallium arsenide I was working with usually needs a coating to emit light efficiently, but to my surprise the emission was strong and the spectra showed features consistent with cavity modes.”

Gallium arsenide is a common material used in photovoltaic cells, lasers and light-emitting diodes (LEDs), but is challenging to work with at the nanoscale as the material requires a surface coating before it will produce light.

“The doped gallium arsenide has a very short carrier lifetime of only a few picoseconds, which means it would be well-suited for use in high speed electronics components,” Mr Burgess said. “The doping has really given these nanolasers a performance edge.”

The new discovery complements ongoing ANU and international efforts to develop nanoscale lasers by demonstrating a new route to increased efficiency and operating speeds, thus providing novel applications in optical telecommunications, quantum computing and biomedical sensing.

Research Group Leader Professor Chennupati Jagadish, from the ANU Research School of Physics Sciences, is thrilled with the possibilities that have opened up as a result of being able to increase 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,” Professor Jagadish said.

Mr Burgess said that the next step will be to integrate these findings into existing nanolaser designs.

“The ultimate aim is to show electrically driven nanolasers operating on a silicon platform compatible with CMOS technologies,” Mr Burgess said. “Using the current results to dramatically improve efficiency will help us get there sooner.”

The research is published in Nature Communications

Image: Tim Burgess loading a wafer into a metalorganic vapour phase epitaxy machine. Courtesy of the Australian National University.