A device that controls the phase of terahertz (THz) radiation has now been developed, reports a paper online this week in Nature Photonics. The ability to manipulate this radiation, which has proved difficult so far, creates opportunities for altering at will a THz laser-beam's intensity, direction of propagation and data-transfer abilities ? features useful in such technologies as imaging and sensing.

The device of Hou-Tong Chen and colleagues is formed from a metamaterial ? a material whose structure provides extra optical properties to those provided by its chemical composition alone. Applying a voltage across the metamaterial changes its properties and allows control over the light that passes through the device. The team also reports broadband THz signal modulation with performance comparable to a commercial mechanical optical chopper, which physically blocks the light beam periodically, while exhibiting drastically superior ? three orders of magnitude so far ? high-speed operation.

Although the THz phase-modulator needs further improvement in performance, this work not only provides a much needed fundamental THz component ? the phase modulator ? but is also a clear example of how metamaterials can offer practical solutions to real-world problems.