Researchers develop efficient laser-beam direction method

‘In many cases, it is much easier to redirect a laser beam at a target than to steer the laser itself. We intended to develop a way to do this efficiently and without moving anything,’ said Dr Michael Escuti, an associate professor of electrical engineering at NC State and co-author of a paper on the research. ‘We also wanted to be able to steer the beams over a wide range of angles, which is important for practical applications.’

To achieve its aims, the team used ‘polarisation gratings’, which consist of a thin layer of liquid-crystal material on a glass plate.

The researchers created a device that allows a laser beam to pass through a stack of these polarisation gratings. Researchers manipulated the optical properties of each grating and were able to steer the laser beams by controlling how each individual grating redirects the light.

‘Because each individual grating is very good at redirecting light in the desired directions with almost no absorption, the stack of gratings does not significantly weaken the laser power,’ said Escuti.

‘Every grating that we add to the stack increases the number of steerable angles exponentially. So not only can we steer lasers efficiently, but we can do it with fewer components in a more compact system,’ said Escuti

‘Compared with other laser-steering technologies, this is extremely cost effective. We’re taking advantage of materials and techniques that are already in widespread use in the liquid-crystal-display sector.’

The technology is said to have a variety of potential applications. For example, free space communication uses lasers to transfer data between platforms — such as between satellites or between an aircraft and soldiers on the battlefield. This sort of communication relies on accurate and efficient laser-beam steering. Other technologies that could make use of the research include laser weapons and LIDAR (laser radar), which uses light for optical scanning applications, such as mapping terrain.

Escuti’s team has already delivered prototypes of the technology to the US Air Force and is currently engaged in additional research projects to determine the technology’s viability for a number of other applications.

The paper, ‘Wide-angle, non-mechanical beam steering with high throughput utilising polarisation gratings’, is published in the journal Applied Optics.