Isaac Asimov was famous for many things, including the fictional application of 'positrons' which surged through the artificial brains of his sci-fi androids.
While positronic brains are still to come, a whirlpool of hybrid light-matter particles called ‘polaritons’ were created by Australian National University (ANU) physicists who engineered this through the creation of a spiral laser beam.
Sending us all into a bit of a spin, Dr Elena Ostrovskaya, a theoretician and leader of the team from the Research School of Physics and Engineering at the ANU said:”Creating circulating currents of polaritons – vortices – and controlling them has been a long-standing challenge.”
“We can now create a circulating flow of these hybrid particles and sustain it for hours.”
So, what exactly are ‘polaritons’?
Continuing, the ANU says that ‘polaritons form in semiconductors when laser light interacts with electrons and holes (positively charged vacancies) so strongly that it is no longer possible to distinguish light from matter.’
And how was this magical-sounding spiral laser beam created by the ANU team?
It was done ‘by putting their laser through a piece of brass with a spiral pattern of holes in it. This was directed into a semiconductor microcavity, a tiny wafer of aluminium gallium arsenide, a material used in LEDs, sandwiched between two reflectors.’
Dr Robert Dall, who led the experimental part of the project, was on the ball when he said: “The vortices have previously only appeared randomly, and always in pairs that swirl in opposite directions,” said Dr Robert Dall, who led the experimental part of the project.”
“However, by using a spiral mask to structure our laser, we create a chiral system that prefers one flow direction. Therefore we can create a single, stable vortex at will.”
Fascinatingly, we’re told that ‘these vortices are an example of quantum fluid behaviour in which the polaritons coalesce into a rare state of matter known as a Bose-Einstein condensate.’
It makes me think that one day this technology could bring Dr Robert Picardo, the emergency medical hologram from Star Trek’s Voyager series to life.
However, before we get too carried away, Dr Ostrovskaya said: “As well as being a window into the quantum world, these polaritonic vortices could be used to construct extremely sensitive detectors of electromagnetic fields, similar to SQUIDS (Superconducting QUantum Interference Devices).”
“They could also be employed as quantum information carriers.”
The ANU also notes that its team ‘has pioneered the study of microcavity polaritons in Australia and hope their success will inspire other research groups around the country.’
“Polaritonics is a rapidly developing research field all around the world. We hope we can build a network of groups researching these devices across Australia and joining the international effort,” Dr Ostrovskaya concluded.