Holy grail of photonic devices achieved with new organic laser tech

31 May 2019

An organic laser diode emitting blue laser light. Image: Atula SD Sandanayaka

Long considered impossible, a new organic laser diode could have a multitude of uses in biosensing, displays, healthcare and optical communications.

A team of researchers in Japan based at Kyushu University has shown that not everything believed to be impossible is so, particularly within the burgeoning field of photonics. In a paper published in Applied Physics Express, it demonstrated that a type of laser diode on organic semiconductors has been achieved.

Long considered a ‘holy grail’ in the area of light-emitting devices, organic laser diodes use carbon-based organic materials to emit light, rather than the industrial reactions produced by the likes of gallium arsenide and gallium nitride.

The effect is similar, in many ways, to organic light-emitting diodes (OLEDs) that produce light in thin layers of organic molecules when electricity is passed through them. Since their discovery, they have grown to dominate the tech industry – and particularly displays – thanks to their high efficiency and vibrancy of colours.

Organic laser diodes, meanwhile, produce a much purer light for significantly greater applications, but require far greater amounts of electricity and have shown instability in devices using them.

‘We finally did it’

As part of this latest research, the team showed that its new technology achieves all of the benefits of organic laser diodes, but with much greater stability and reduced electricity demands.

“I think that many people in the community were doubting whether we would actually one day see the realisation of an organic laser diode,” said Atula SD Sandanayaka, lead author on the paper, “but by slowing chipping away at the various performance limitations with improved materials and new device structures, we finally did it.”

To overcome the issue of high resistance to electricity in organic materials, the team used a highly efficient organic light-emitting material. Then, it designed a device structure with a grid of insulating material on top of one of the electrodes used to inject electricity into the organic thin films.

The group’s leader, Chihaya Adachi, said: “By optimising these grids, we could not only obtain the desired optical properties but also control the flow of electricity in the devices and minimise the amount of electricity required to observe lasing from the organic thin film.”

Colm Gorey was a senior journalist with Silicon Republic