It's a breakthrough because the researchers are able to modify and control the signal continuously, says Xi-Cheng Zhang, director of the Terahertz Center for Research at Rensselaer Polytechnic Institute, in Troy, NY.

Ultimately, the researchers hope to manipulate terahertz waves much the same way they focus, filter, and switch laser beams to encode information onto the signal. Chen and his colleagues have laid the foundation, says Zhang, but he adds that there is still a long way to go.

In practical terms, this should translate into big changes in terahertz devices. For example, they might help enhance the blurry images currently produced by passive terahertz detectors.

Creating filters that can tune to particular frequency ranges may also improve devices designed to detect explosives, says Don Arnone, chief executive of Teraview. Allowing such devices to isolate specific narrow bands of terahertz may prove to be an easier way to detect the chemical signatures for explosives.

According to Chen, the metamaterials could be useful for improving terahertz lenses, but he believes the real benefits will be in wireless communications. Modulation is the very principle that underpins communications. Chen says that by demonstrating that they can modulate a terahertz signal, the researchers have shown that it is possible to encode information on a terahertz carrier wave.

Zhang agrees. There is a natural progression to move beyond microwaves and into the terahertz band. While terahertz are useless for long-range communications because they are so easily absorbed by atmospheric water, the improvements in speed and bandwidth they offer make it almost inevitable that terahertz will be used for short-range communications. "Sooner or later, we're going to have terahertz communications," Zhang says.