The First "Metatronic" Circuit

  • Published
  • By Robert White
  • Office of Scientific Research
ARLINGTON, Virginia --  The Air Force Research Laboratory is supporting University of Pennsylvania researchers who are pushing circuitry forward in a radically different way: replacing electricity with light. The Penn research group has created the first physical demonstration of "lumped" optical circuit elements, representing a milestone in a nascent field of science and engineering dubbed "metatronics."

In electronics, the "lumped" designation refers to elements that can be treated as a black box, something that turns a given input to a predictable output. Nanotechnology has opened the possibility for lumped optical circuit elements, allowing construction of structures that have dimensions measured in nanometers. In this experiment's case, the structure comprised comblike arrays of rectangular nanorods made of silicon nitrite.

The researchers illuminated the nanorods with an optical signal, a wave of light in the mid-infrared range. They then used spectroscopy to measure the wave as it passed through the comb. Repeating the experiment using nanorods with nine different combinations of widths and heights, the researchers showed that the optical "current" and optical "voltage" were altered by the optical resistors, inductors and capacitors with parameters corresponding to those differences in size. A section of the nanorod acts as both an inductor and resistor, and the air gap acts as a capacitor. Beyond changing the dimensions and the material the nanorods are made of, the function of these optical circuits can be altered by changing the orientation of the light, giving metatronic circuits access to configurations that would be impossible in traditional electronics. This is because a light wave has polarizations; the electric field that oscillates in the wave has a definable orientation in space. In metatronics, it is that electric field that interacts and is changed by elements, so changing the field's orientation can be like rewiring an electric circuit.

Nanotechnology has opened the possibility for lumped optical circuit elements, which allows construction of structures that have dimensions measured in nanometers. The function of optical circuits can be altered by changing the orientation of the light, giving metatronic circuits access to configurations that would be impossible in traditional electronics.

Modern technology owes a great deal to advances in electrical engineering, specifically, the ability to finely control the flow of electrical charges using increasingly small and complicated circuits. As Penn researcher Nader Engheta notes, "If we moved to shorter wavelengths in the electromagnetic spectrum--like light--we could make things smaller, faster and more efficient."