New Terahertz Chips For New Devices
December 10, 2012

New Terahertz Chips Enable Next Generation Of Devices

Lee Rannals for — Your Universe Online

A new set of microchips designed at the California Institute of Technology pave the way for a new generation of devices.

The chips created by the Caltech engineers generate and radiate high-frequency electromagnetic waves known as terahertz (THz). These waves fall between microwaves and far-infrared radiation and are able to penetrate materials without damaging them, unlike X-rays.

The new microchips could be incorporated into handheld devices in the future to enable a broad range of applications; anything from homeland security devices to health care.

Engineers say the technology could help lead to noninvasive cancer diagnosis in the health industry, or simple, handheld bomb-detection devices.

"Using the same low-cost, integrated-circuit technology that's used to make the microchips found in our cell phones and notepads today, we have made a silicon chip that can operate at nearly 300 times their speed," Ali Hajimiri, the Thomas G. Myers Professor of Electrical Engineering at Caltech, said in a statement. "These chips will enable a new generation of extremely versatile sensors."

Electronics working in the terahertz frequency range can penetrate packaging materials and detect the chemical fingerprints of pharmaceutical drugs, biological weapons, or illegal drugs and explosives.

Most terahertz systems today require a bulky and expensive laser setup, so the potential of terahertz imaging and scanning has been limited.

Caltech researchers used complementary metal-oxide semiconductor, or CMOS technology, to design silicon chips with fully integrated functionalities and that operate at terahertz frequencies.

"This extraordinary level of creativity, which has enabled imaging in the terahertz frequency range, is very much in line with Caltech's long tradition of innovation in the area of CMOS technology," Ares Rosakis, chair of Caltech's Division of Engineering and Applied Science, said in the statement. "Caltech engineers, like Ali Hajimiri, truly work in an interdisciplinary way to push the boundaries of what is possible."

The new chips push out signals that are a thousand times stronger than existing approaches and emanate terahertz signals that can be programmed to point in a specific direction.

The researchers used their scanner to reveal a razor blade hidden within a piece of plastic and have also determined the fat content of chicken tissue.

"We are not just talking about a potential. We have actually demonstrated that this works," Hajimiri said. "The first time we saw the actual images, it took our breath away."

The team had to overcome multiple hurdles to translate CMOS technology into workable terahertz chips, including finding a way to work past the cut-off frequency all transistors face.

In order to work around the cut-off-frequency problem, the researchers harnessed the collective strength of many transistors operating in unison. If multiple elements are operated at the right times, their power can be combined, boosting the strength of the collective signal.

"We came up with a way of operating transistors above their cut-off frequencies," added postdoctoral scholar Kaushik Sengupta. "We are about 40 or 50 percent above the cut-off frequencies, and yet we are able to generate a lot of power and detect it because of our novel methodologies."

Hajimiri said typically people have tried to make these technologies work at high frequencies with large elements producing the power. However, now they were able to make a large number of transistors that can be combined to do a lot more.

"If these elements are synchronized–like an army of ants–they can do everything that the elephant does and then some," Hajimir explained.

The engineers also figured out how to radiate the terahertz signals once they have been produced, devising a way to turn the whole silicon chip into an antenna.

"We had to take a step back and ask, 'Can we do this in a different way?'" Sengupta said. "Our chips are an example of the kind of innovations that can be unearthed if we blur the partitions between traditional ways of thinking about integrated circuits, electromagnetics, antennae, and the applied sciences. It is a holistic solution."