Laser-like beam may break barriers to technological progress

Researchers in the US have created a sharply focused, laser-like beam of ultraviolet light that could be used to measure and manipulate nanoscale objects.

Researchers at the University of Colorado have created a sharply focused, laser-like beam of ultraviolet light using a device that could fit on a dining room table. Scientists and engineers will be able to use this extreme ultraviolet (EUV) light source to measure and manipulate nanoscale objects.

Size is said to have been a major hurdle to developing, or even seeing, the tiny components for next-generation computers and nanoscale machines because the objects can be smaller than the waves of light illuminating them.

While electron microscopes and other scanning devices can view the small structures, many critical measurements require optical microscopes, and optics are limited by the wavelength of their light sources.

The EUV light, which has a wavelength of only tens of nanometres, can pulse in shorter bursts than any other system on the planet (a critical property for measuring fast interactions between small particles) and has a tight focus that is difficult to achieve with other EUV sources.

The researchers used a process called high harmonic generation (HHG) to produce the EUV light. To achieve HHG, the researchers fired a visible-light laser into a gas, creating a strong electromagnetic field. The field ionises the gas, separating the electrons from their parent atoms.

The electrons re-collide with the ionised gas atoms and oscillate back and forth within the electromagnetic field. As a result, a well-synchronised stream of photons fires out of the system, boosted up to a high-energy, extreme ultraviolet wavelength.

The end product is a multi-megawatt laser, except it was not created through direct stimulated emission of radiation.

The EUV beam is so focused that, in the right system, it could produce the smallest diameter laser-like beam in the world – 20 to 30 times smaller than a more common helium-neon laser and several hundred times more intense.

The team used a visible-light laser that can fire in bursts as short as a femtosecond, yet their breakthrough development is a ‘structured waveguide’ that confines the target gas and keeps the EUV beam steady and tightly focused. The resulting conversion of visible laser light into EUV wavelengths is more than a hundred times more efficient than other laser designs.

Already, said team member Henry Kapteyn, the EUV light will have applications for basic science, such as observing the behaviours of molecules, and soon may assist engineers as they align and test manufacturing systems. The light may also prove useful for creating high-resolution biological holograms, taking the role of a tabletop-sized mini-synchrotron for some applications, said Kapteyn.

‘In an arena such as microelectronics, any new tool that speeds development of a new technology can have a big economic and competitive impact,’ said Kapteyn. The team has since commercialised the femtosecond laser and is in the process of commercialising their EUV beam.