Already the first crude images from terahertz image chips have proven that Superman-style "X-ray vision" may soon be commonplace. Last year the European Space Agency's StarTiger R&D team showed a 16-pixel device that they claim produced the world's first terahertz picture of a human hand. The detector used a silicon photonic-bandgap material.
Likewise, microelectromechanical systems are also being crafted to bridge the terahertz gap. At least one group has built a stack of silicon bars with a micromachined funnel that focuses terahertz signals of 1- to 10-micron wavelengths. Both traditional- and quantum-transistor experimenters have also reported progress. Intel Corp., for one, promises a "terahertz" transistor later in this decade using silicon-on-insulator technology, a fully depleted substrate and a high-k gate dielectric.
Academic researchers are also chalking up advances in the solid-state use of terahertz signals. Roland Kersting at Rensselaer Polytechnic Institute has a resonant detector operating in the terahertz range using an AlGaAs/GaAs 0.15-µm gate FET.
Likewise, nanotechnology experts are on the case. Michael Fuhrer and colleagues at the University of Maryland's Center for Superconductivity Research predict that silicon combined with nanotubes will enable terahertz carbon-nanotube transistors. Researchers at the Delft University of Technology in the Netherlands, meanwhile, claim to have developed the world's first SRAM with carbon-nanotube transistors. The team predicts it will achieve terahertz speeds soon. IBM Corp., too, claims that its carbon-nanotube transistors will eventually operate at terahertz speeds. And the Defense Advanced Research Projects last month accepted proposals for its Terahertz Imaging Focal Plane Array Technology program (www.fedgrants.gov/Applicants/DOD/DARPA/CMO/BAA04-07).
Even metamaterials experts are getting in on the act. For instance, University of California at San Diego physicists David Smith, Richard Shelby and Sheldon Schultz recently showed integrated 50-µm SRRs that respond to the terahertz signal's magnetic component. "Bridging the terahertz gap will be important for automated inspection, zero-visibility weather conditions, biomedical imaging and security applications," said UCSD doctoral candidate Willie Padill.
Now that the UCSD team has shown that millimeter-size patterns on circuit boards for microwave reception can be downsized to micron-size patterns on chips, it may be only a matter of time until chip-size SRR-based sensors in airports "see through" your clothing and baggage to identify weapons and explosives.