Getting warmer -- Leeds research brings terahertz closer to everyday use

“We hope to obtain further advances by optimising the methods we used to create the device,” explains Professor Linfield. “We have some radically new design ideas, and also believe that we can make significant improvements in the way we fabricate the lasers.”

Terahertz quantum cascade lasers are created by building layers of compounds of aluminium, gallium and arsenic one atomic monolayer at a time, through a process known as molecular beam epitaxy. Leeds’ Faculty of Engineering is one of a small number of laboratories in the world actively ‘growing’ terahertz quantum cascade lasers at this time, using a molecular beam epitaxy system purchased through the Science Research Infrastructure Fund (SRIF).

In molecular beam epitaxy, the chemicals evaporate from heated cells, and land on a heated, rotating, substrate. Minute changes in temperature, combined with a set of shutters that block the chemical beams, enable the team to adjust the amount of each chemical which is deposited on the substrate, gradually building up the layers they need. To ensure the device works perfectly, there must be no pollutants, so the process is carried out under ultra-high vacuum conditions, approaching the vacuum levels found in outer space.

The equipment and expert use of it by Professor Linfield and his team enabled them to create a device of superior quality. They now believe that they can bring handheld terahertz technology a step closer still.

The research, carried out in collaboration with the group of Professor Frederico Capasso at Harvard University, and supported by the Engineering and Physical Sciences Research Council (EPSRC) is published in Optics Express ( Vol. 16, Issue 5, pp. 3242-3248).