MIT Sees the Light on Optical Chips

MIT researchers are one step closer to creating photonic chips that use light beams instead of electrons to perform computational tasks. The research team developed a light-based diode that could lead to a low-cost way to create integrated optical circuits.

MIT’s research team published a paper on the new device in the journal Nature Photonics in November.

We already use fiber optics for communication systems, but when data reaches a computer the information has to be converted to electronic form to be processed, then changed back to light again. The folks at MIT were looking for a way to skip that conversion step in order to increase efficiency.

A photonic chip could transfer information at the speed of light, and could someday allow engineers to work in the cloud without worrying about broadband bottlenecks.

The challenge:

Non-reciprocal photonic devices, including optical isolators and circulators, are indispensible components in optical communication systems. However, the integration of such devices on semiconductor platforms has been challenging because of material incompatibilities between semiconductors and magneto-optical materials that necessitate wafer bonding, and because of the large footprint of isolator designs.

The new advancement is MIT’s “diode for light,” which creates a one-way path for light, similar to the way an electric diode allows current to flow in one direction but not the other in a traditional diode. These devices would prevent stray reflections from destabilizing the lasers used to produce optical signals and reducing transmission efficiency in a photonic chip.

MIT Professor Caroline Ross helped develop the new "diode for light." Image Source: MIT

The MIT team used garnet to create the light diode. Garnet is both transparent and magnetic, and inherently transmits light differently in one direction. The researchers deposited a thin film of garnet covering one half of a loop connected to a light transmitting channel on the chip. Light traveling through the chip in one direction passes through, while light going the other way is divereted into the loop.

The technology can boost the speed of data transmission because light travels faster than electrons, and optical computing devices can transmit multiple beams of light (carrying separate data streams) simultaneously.

Even better, the system can be made using standard microchip manufacturing equipment.

“A silicon platform is what you want to use [because] there’s a huge infrastructure for silicon processing. Everyone knows how to process silicon. That means they can set about developing the chip without having to worry about new fabrication techniques.” — Caroline Ross, Toyota Professor Materials Science and Engineering at MIT

IBM, Intel and other companies are already working on optical chip projects, too.

You can watch a video about IBM’s work on photonics below:

Source: MIT

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