Cornell researchers have created a broadband light amplifier on a silicon chip, a major breakthrough in the quest to create photonic microchips.

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 only 300 x 550 nanometers (nm = a billionth of a meter, about the length of three atoms in a row) wide, smaller than the wavelength of the infrared light traveling 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 fiber-optic communications, where several different wavelengths are sent over a single fiber at the same time. The new broadband device makes it possible to amplify the multiplexed traffic all at once.

The process also creates a duplicate signal at a different wavelength, so the devices could be used to convert a signal from one wavelength to another.

Although four-wave mixing amplifiers have been made with optical fibers, such devices are tens of meters long. Researchers are working to create photonic circuits on silicon because silicon devices can be manufactured cheaply, and photonics on silicon can easily be combined with electronics on the same chip.

Source: Cornell University news releease