Getting wired for terahertz computing

“We have demonstrated the ability to do this, which is a necessary requirement for making terahertz guided-wave circuits,” Nahata says.

Circuits: From Electrical to Optical to Terahertz

Wires act as waveguides for electricity. Wires connect active devices such as transistors, which switch or adjust the electric signal. That is the basis for how computers work today. An electronic integrated circuit is a computer processor made of wires, transistors, resistors and capacitors on a semiconductor chip made of silicon.

In optical communications, the waveguides carry laser-generated light in fiberoptic cables and lines etched or deposited on an insulator or semiconductor surface. Nahata says photonic integrated circuits now are used for phone and Internet communications, mainly for combining or “multiplexing” different colors or channels of light entering a fiber-optic cable and separating or “demultiplexing” the different wavelengths exiting the cable.

“Electronic circuits today work at gigahertz frequencies – billions of cycles per second. Electronic devices like a computer chip can operate at gigahertz,” Nahata says. “What people would like to do is develop capabilities to transport and manipulate data at terahertz frequencies [trillions of hertz.] It’s a speed issue. People want to be able to transfer data at higher speeds. People would like to download a movie in a few seconds.”

“In this study, we’ve demonstrated the first step toward making circuits that use terahertz radiation and ultimately might work at terahertz speeds,” or a thousand times faster than today’s gigahertz-speed computers, Nahata says.

Channeling, Bending, Splitting and Coupling T-Rays

“People have been working on terahertz waveguides for a decade,” he says. “We’ve shown how to make these waveguides on a flat surface so that you can make circuits just like electronic circuits on silicon chips.”

The researchers used pieces of stainless steel foil about 4 inches long, 1 inch wide and 625 microns thick, or 6.25 times the thickness of a human hair. They perforated the metal with rectangular holes, each measuring 500 microns (five human hair widths) by 50 microns (a half a hair width). The rectangular holes were arranged side by side in three different patterns to form “wires” for terahertz radiation:

• One line of rectangles that served as a “wire” and carried terahertz radiation.
  
  

• A line that becomes two lines – like the letter Y – to split the far-infrared light, similar to a splitter used to route a home cable TV signal to separate television sets.