Surface plasmons can only exist in a metal/dielectric interface. They are electromagnetic waves that run along the surface of this interface. “What we wanted to do,” explains Zhang, “is start with a non-conductive material to see if we could excite surface plasmons in the terahertz region.” For their attempt, Zhang and his colleagues use silicon because of its properties as a semiconductor. “We used ultra-fast laser pulses that resulted in photodoping.”
Biomedicine is a field especially where terahertz systems can find good use. Terahertz radiation can be used to “look” deep inside organic materials, and they do it without causing the damage that X-rays do. Additionally terahertz radiation is being considered for use in screening airport passengers.
Zhang also points out that surface plasmon resonance to direct terahertz systems can also be used to enhance space communication: “This would be ideal for making tunable switches.” Indeed, astronomers are interested in using terahertz technology to study the particles that fall into the category of “far-infrared.”
“Because silicon is cheap, rigid, and tunable,” concludes Zhang, “this is an important and exciting finding. The applications for technology are just beginning.”