Circuits that run on light

Engineers at the University of Pennsylvania have theorised a means of shrinking electronics so they could be run using light instead of electricity.

In the search to create faster, smaller and more energy-efficient electronics, researchers have looked elsewhere in the electromagnetic spectrum, which ranges from the low-frequency energy used in everyday electronics to the high-frequency energy of gamma rays, to pass the limits of conventional technology.

The Penn theorists outline how familiar circuit elements - inductors, capacitors and resistors - could be created on the nanoscale to operate using infrared or visible light.

The researchers describe how nanoscale particles of certain materials, depending on their unique optical properties, could work as circuit elements.

For example, nanoscale particles of certain metals, such as gold or silver, could perform the same function in manipulating an 'electric' current as an inductor does on a circuit board.

Optical electronics would make it possible to create faster computer processors, construct nanoscale antennas or build more information-dense data-storage devices. Optical electronics could also have exotic applications that are not possible with conventional electronics, such as the ability to couple an electronic signal to an individual molecule or the creation of biological circuits.

According to their models, the theorists demonstrated that a nano-sized sphere made up of a nonmetallic material such as glass with permittivity greater than zero would act like a miniaturised capacitor. A nano-sized sphere made up of a metallic material such as gold or silver with a permittivity less than zero would act like a miniaturised inductor. Either material could also function like a miniaturised resistor, depending on how the optical energy is lost in it.