Terahertz waves can now be created and detected with microchips small enough to fit on a fingertip, as opposed to a tabletop setup with lasers and mirrors.
Kaushik Sengupta, an assistant professor of electrical engineering at Princeton University, says they have developed a pair of chips, one that can generate terahertz waves, and a second that can capture and read intricate details of these waves.
"The system is realised in the same silicon chip technology that powers all modern electronic devices from smartphones to tablets, and therefore costs only a few dollars to make on a large scale" he said.
Terahertz waves sit between the microwave and infrared light wavebands on the electromagnetic spectrum. They have some unique characteristics that make them interesting to science. They pass through most non-conducting material, so they could be used to peer through clothing or boxes for security purposes, and because they have less energy than X-rays, they don't damage human tissue or DNA. They may hold the key to advances in medical imaging, communications and drug development.
Sengupta's team discovered a way to reduce the size of the terahertz generator and the apparatus that interprets the returning waves to a millimeter-sized chip. The solution lies in re-imaging how an antenna functions. When terahertz waves interact with a metal structure inside the chip, they create a complex distribution of electromagnetic fields that are unique to the incident signal. Typically, these subtle fields are ignored, but the researchers realised that they could read the patterns as a sort of signature to identify the waves. The entire process can be accomplished with tiny devices inside the microchip that read terahertz waves.
"Instead of directly reading the waves, we are interpreting the patterns created by the waves," Sengupta said. "It is somewhat like looking for a pattern of raindrops by the ripples they make in a pond."
On the terahertz-generation end, much of the challenge is creating a wide range of wavelengths within the terahertz band, particularly in a microchip. The researchers realised they could overcome the problem by generating multiple wavelengths on the chip. They then used precise timing to combine these wavelengths and create very sharp terahertz pulses.
[Photo: Frank Wojciechowski/Princeton]