Light-controlling devices known as interferometers could become basic building blocks of future optics-based computers and devices similarly to semiconductors in current electronics, researchers have suggested.
Writing in the journal Optica, a team of researchers from California’s Stanford University described how meshes of a specific type of interferometers, the Mach-Zehnder interferometers, could be used in optical devices providing what they call ‘perfect performance’.
"Recently, optical researchers have begun to understand that these interferometers can be thought of as universal 'building blocks' that could enable us to construct essentially any optical device we could imagine," said the author of the paper David A.B. Miller.
Mach-Zehnder interferometers are used to split light into two beams and then recombine them. They are currently being used for switching beams in optical communication in optical fibres. However, to use them in computing would require them to perform perfectly, splitting the beams with flawless symmetry, which is never the case. As a result engineers can’t completely control the optical paths using just one such interferometer.
However, the approach proposed by the Stanford team would allow making up for those imperfections by using a whole mesh of interferometers. If properly programmed, this mesh, or array, would compensate for the imperfections of its individual components.
"It's this larger scheme that allows us to use reasonable but imperfect versions of these components," explains Miller.
Optical technologies have the potential to greatly reduce the power consumption of computers, speed up telecommunications, and enhance the sensitivity of chemical and biological sensors. Currently, they mostly use mirrors and lenses to transmit the optical signals. These component, however, have many limitations. First of all they can’t be scaled to the minuscule sizes required for electronics applications, something that would be possible with interferometers.
The researchers said meshes of Mach-Zehnder interferometers could essentially perform any so-called ‘linear’ optical operation, much like computers are able to perform any logical application by controlling on/off functions of semiconductors.
Using smart software, the meshes could be able to automatically adjust the direction of light paths based on received signals.
This self-correcting algorithm allowed the researchers to propose meshes of interferometers with some imperfections and then compensate to make them behave as if they were perfect.
"With this development, we are starting to do some things in optics that we have been doing in electronics for some time," observed Miller. "By using small amounts of electronics and novel algorithms, we can greatly expand the kinds of optics and applications by making completely custom optical devices that will actually work."