Engineers at Cornell have developed a new method of generating terahertz signals on an inexpensive silicon chip, that may be useful in applications such as medical imaging and wireless data transfer.
Terahertz radiation, the portion of the electromagnetic spectrum between microwaves and infrared light, penetrates cloth and just a few millimeters into the skin, but without the potentially damaging effects of X-rays. It can be used to identify skin cancers too small to see with the naked eye.
While current methods of generating terahertz radiation involve lasers, vacuum tubes, and special circuits cooled near absolute zero, Ehsan Afshari, assistant professor of electrical and computer engineering, developed a new method using inexpensive CMOS chip technology, generating power levels high enough for some medical applications.
The ability of solid-state devices to generate high frequencies is limited by the characteristics of the material — basically, how fast electrons can move back and forth in a transistor. So circuit designers make use of harmonics — signals that naturally appear at multiples of the fundamental frequency of an oscillator. Afshari has discovered a new way of tuning by coupling several oscillators in a ring, producing what engineers call a high-quality signal, where all the power goes into a very narrow frequency band.
