Getting wired for terahertz computing

• Two lines that curve close to each other in the middle – like an X where the two lines come close but don’t touch – so the radiation could be “coupled,” or moved from one line or “wire” to another.
  
  

The straight pattern successfully carried terahertz radiation in a straight line. The other two patterns “changed the direction the terahertz radiation was moving” by splitting it or coupling it, Nahata says. The study showed the terahertz radiation was closely confined both vertically (within 1.69 millimeters of the foil’s surface) and horizontally (within 2 millimeters of the pattern of rectangles as it moved over them).

“All we’ve done is made the wires” for terahertz circuits, Nahata says. “Now the issue is how do we make devices [such as switches, transistors and modulators] at terahertz frequencies"”

When terahertz radiation is fed into the stainless steel waveguides, it spans a range of frequencies. One frequency is guided across the steel surface. That frequency is determined by the size of perforations in the foil. The engineers chose a frequency they could generate and measure: about 0.3 terahertz, or 300 gigahertz. Terahertz radiation is defined as ranging from 0.1 terahertz (or 100 gigahertz) to 10 terahertz.

The design of the waveguide means that it carries terahertz radiation in the form of surface plasma waves – also known as plasmons or plasmon polaritons – which are analogous to electrons in electrical devices or photons of light in optical devices. The surface plasma waves are waves of electromagnetic radiation at a terahertz frequency that are bound to the surface of the steel foil because they are interacting with moving electrons in the metal, Nahata says.

Nahata’s department is part of the University of Utah’s College of Engineering, which has six academic departments plus a School of Computing, with a total of 130 full-time faculty members, 2,047 undergraduate students and 812 graduate students.

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Contacts:

• Ajay Nahata, associate professor of electrical and computer engineering – cellular (801) 809-1392, office (801) 581-5184,

• Lee Siegel, science news specialist, University of Utah Public Relations – office (801) 581-8993, cellular (801) 244-5399,