Electron microscope image of a prototype chip using a ring of coupled oscillators to generate terahertz radiation. Silicon cannot oscillate in the terahertz range, but the design focuses most of the energy in a high harmonic. The signal radiates on the axis of the ring and can be aimed.
Cornell researchers have developed a new method of generating terahertz signals on an inexpensive silicon chip, offering possible applications in medical imaging, security scanning and wireless data transfer. Terahertz radiation, the portion of the electromagnetic spectrum between microwaves and infrared light, penetrates cloth and leather and just a few millimeters into the skin, but without the potentially damaging effects of X-rays. Terahertz scanning can identify skin cancers too small to see with the naked eye. Many of the complex organic chemicals used in explosives absorb terahertz radiation at particular frequencies, creating a "signature" that detectors can read. And because higher frequencies can carry more bandwidth, terahertz signals could make a sort of super-Bluetooth that could transfer an entire high-definition movie wirelessly in a few seconds. Current methods of generating terahertz radiation involve lasers, vacuum tubes and special circuits cooled near absolute zero, often in room-sized apparatus costing thousands of dollars. Ehsan Afshari, assistant professor of electrical and computer engineering, has developed a new method using the familiar and inexpensive CMOS chip technology, generating power levels high enough for some medical applications.
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