Four-wave mix

researchers have created a broadband light amplifier on a silicon chip, a major breakthrough in the quest to create photonic microchips. In such microchips, beams of light travelling through microscopic waveguides will replace electric currents travelling through microscopic wires.

A team of researchers working with Alexander Gaeta, Cornell professor of applied and engineering physics, and Michal Lipson, assistant professor of electrical and computer engineering, used the Cornell NanoScale Facility to make the devices.

The amplifier uses a phenomenon known as four-wave mixing, in which a signal to be amplified is ‘pumped’ by another light source inside a very narrow waveguide. The waveguide is a channel 300 x 550 nanometres (nm) wide, smaller than the wavelength of the infrared light travelling through it. The photons of light in the pump and signal beams are tightly confined, allowing for transfer of energy between the two beams.

The advantage this scheme offers over previous methods of light amplification is that it works over a fairly broad range of wavelengths. Photonic circuits are expected to find their first applications as repeaters and routers for fibre-optic communications, where several different wavelengths are sent over a single fibre at the same time. The new broadband device makes it possible to amplify the multiplexed traffic all at once.