New kind of laser uses tiny particle clumps to generate light

Lasers normally use mirrors to create laser light, but a new kind uses clumps of moving particles. The result is a laser that is more programmable and could generate extra sharp visual displays

By Karmela Padavic-Callaghan

A new kind of laser uses tiny moving particles to produce beams of light. The laser is more programmable than standard lasers and the approach could be used to create visual displays that are sharp from all angles.

Conventional lasers repeatedly bounce light between two mirrors until it becomes bright and focused. Riccardo Sapienza at Imperial College London and his colleagues have built a laser that uses particles that can arrange themselves to carry out a similar process.

The new type of laser first requires the use of green light from a traditional laser. The researchers shine this green light into a small glass box filled with a liquid solution containing titanium oxide and silicone oxide particles. This warms up the silicone oxide particles and causes the titanium oxide particles to clump around them.

The green light then bounces between particles in the clump – similarly to how light bounces between mirrors in conventional lasers – until the clump itself starts to emit a laser beam, now in the colour red.

By nudging the particles into different positions with the green light, the team can them program the properties of the light emitted by the laser, such as where in the device it originates from and how pure its colour is. By comparison, conventional lasers can’t be adjusted after manufacturing.

Diederik Wiersma at the University of Florence in Italy says that the new laser is the first kind to be programmed by moving its components, which allows it to have multiple functions.

Sapienza says one use may be in display screens, such as digital billboards. Particles could move and assemble at a specific location within the display and emit a colour that could be very pure, visible in both very bright and very dim light and from all lines of sight.

In the future, he wants to devise a way for particles to move around the solution autonomously and start emitting laser light once they encounter a contaminant or some other environmental change like higher acidity. He says that such a sensing device would be a little like a “living laser”, exploring its environment and changing its shape so that it can signal when it comes across something dangerous.

Journal reference: Nature Physics, DOI: 10.1038/s41567-022-01656-2