April 27, 2006, Houston, TX--Frequently, the unexpected results in science are the most exciting. That's the case with the latest findings from the lab of Rice University's electrical engineer Daniel Mittleman, who was trying to find new ways to use terahertz energy, or T-rays, for chemical sensing when he noticed a strange tendency of the signals to travel slower if they were sent down smaller metal wires.
Mittleman and graduate student Kanglin Wang reported their findings in the April 21 issue of Physical Review Letters. Their explanation for the odd phenomenon arises from the unique way that T-rays interact with the sea of electrons flowing across the surface of the metal wire.
"A similar variation in wave velocity is well-documented for higher frequency radiation in the visible portion of the spectrum, but this was a real puzzle because no one had predicted it for such low frequencies," said Mittleman, associate professor of electrical and computer engineering.
Mittleman and Wang discovered that the phenomenon during follow-up experiments to last year's development of T-ray wire waveguides. Their discovery that T-rays propogate down bare metal wires has allowed them to make T-ray endoscopes that can carry T-rays around corners and into tight places like pipes and metal containers, where it hasn't been feasible to place a T-ray generator. Mittleman hopes to use the technique to design a new class of chemical sensors that port security officers can use to quickly determine whether explosives are hidden inside shipping containers.