Physicists Create Quantum Whirlpool with a Spiral Laser Beam

Physicists have made a breakthrough with lasers. They've engineered a spiral laser beam and used it to create a whirlpool of hybrid light-matter particles called polaritons.

Polaritons are hybrid particles that have properties of both matter and light. The ability to control polariton flows in this way could actually aid the development of completely novel technology to link conventional electronics with new laser and fiber-based technologies.

"Creating circulating currents of polaritons-vortices-and controlling them has been a long-standing challenge," said Elena Ostrovskaya, one of the researchers, in a news release. "We can now create a circulating flow of these hybrid particles and sustain it for hours."

So how did the researchers create the spiral beam in the first place? They put their laser through a piece of brass with a spiral pattern of holes in it. This was then directed into a semiconductor microcavity, which was a tiny wafer of aluminum gallium arsenide, which is a material used in LEDs, sandwiched between two reflectors.

"The vortices have previously only appeared randomly, and always in pairs that swirl in opposite directions," said 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."

The polaritonic vortices don't just give researchers a view into the quantum world. They could also be used to construct extremely sensitive detectors of electromagnetic fields. In addition, they could be used as quantum information carriers.

"Polaritonics is a rapidly developing research field all around the world," said Ostrovskaya. "We hope we can build a network of groups researching these devices across Australia and joining the international world."

The findings are published in the journal Physical Review Letters.