Scientists demonstrate terahertz semiconductor laser

The advance, for which Harvard has filed a patent, could lead to a range of applications in terahertz science and technology.

THz rays (T-rays) can penetrate paper, clothing, plastic and many other materials, making them ideal for detecting concealed weapons and biological agents, imaging tumours without harmful side-effects, and spotting defects, such as cracks, within materials. THz radiation is also used for high-sensitivity detection of tiny concentrations of interstellar chemicals.

However, traditional systems for generating and detecting T-Rays are expensive, often costing in excess of £100,000.

Federico Capasso, from Harvard’s School of Engineering and Applied Sciences, said: ‘Unfortunately, present THz semiconductor lasers are not suitable for many of these applications because their beam is widely divergent — similar to how light is emitted from a lamp. By creating an artificial optical structure on the facet of the laser, we were able to generate highly collimated [tightly bound] rays from the device. This leads to the efficient collection and high concentration of power without the need for conventional, expensive, and bulky lenses.’