Researchers from the University of Strathclyde and Capital Normal University in Beijing have developed a new form of terahertz (THz) radiation, which could enable medical images to be produced more safely than conventional X-rays.

In the article ‘High-energy coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator’, published in the New Journal of Physics, the team explains how the radiation’s ability to carry ultra-high bandwidth communications enables it to detect molecules.

“This is an unprecedented efficiency at these THz energies,” said director of the Scottish Centre for the Application Plasma-based Accelerators, which initiated the project, Professor Dino Jaroszynski. “The increasing availability of intense THz sources will lead to completely new avenues in science and technology.”

THz radiation is far-infrared electromagnetic radiation with a frequency between 0.1 THz and 10 THz. The vibrational and rotational properties of the radiation enable it to identify hazardous substances, such as drugs.

Many biological macromolecules, such as DNA and proteins, experience movement at THz frequencies, and so would be most accurately documented using THz radiation. The radiation can also be used to observe semiconductors and nanostructures, and so is an important tool for developing new electro-mechanical devices, which could include medical implants.

THz can be generated in a number of ways, including driving photocurrents in semiconductor antennas, but its maximum power is restricted due to the potential for damage of optical materials. If plasma is used, however, this restriction is limited as it is already broken. Jaroszynski’s team was able to use the high-charge and low-energy electron bunches to efficiently transfer laser energy to an intense pulse of THz radiation.

“Since the charge of wide-angle beams increases linearly with laser intensity and plasma density, the energy of THz radiation will scale to milijoule-levels, which would make an intense source of THz radiation with peak powers in excess of GW, which is comparable with that of a far-infrared free-electron laser,” said Dr Enrico Brunetti of Strathclyde’s department of physics.