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IBM Research Announces First-Ever Room Temperature All-Optical Transistor

The breakthrough could lead to the faster operations and lower power that technologies like artificial intelligence, edge and quantum computing will require in the coming years.

• By Becky Nagel
• 05/24/2019

Optical (or photonic) computing -- where internal circuits use light instead of electricity to function -- has been the goal of many in the computing world for decades, as it's estimated that optical computations could run up to 10 times faster than those powered by electric current, plus consume less energy overall. But there are numerous technical (and cost) challenges to creating a purely optical computer.

One of those challenges is the transistor itself. Previously, according to IBM, researchers had created an inorganic transistor that was capable of 100 percent optical transition; however, it required cryogenic cooling to operate and the light signal amplification was lacking.

On Friday, May 24, however, IBM researchers from a lab in Zürich announced online and in the journal Nature Photonics that they have created in partnership with the Skolkovo Institute of Science and Technology an all-optical, organic-based transistor that can run at room temperature and provides light amplification "330 times higher than the amplification attained by its inorganic counterpart."

IBM also pointed out that the transistor "allows for cascadability, which is a necessary condition to use the transistor for logic gates. In experiments, our device also exhibited the highest net optical gain ever observed for an optical transistor (~10 dB/micrometer)."

The transistor is made from an organic semiconducting polymer (methyl-substituted ladder-type poly- [paraphenylene] or MeLPPP) supplied by Wuppertal University. "We placed a 35 nanometer-thin layer of MeLPPP between two highly reflective mirrors to form an optical cavity in which exciton-polaritons were produced using a laser," the researchers explained. "An exciton-polariton consists in the superposition of an exciton (an electron-hole pair) and a photon. That's why our device falls in the category of organic polariton transistors."

According to the researchers, the fact that the transistor is organic is key:

In inorganic polariton microcavities, the pump laser used to trigger the transistor response must be directed at the device under certain angles only. In our organic device, there's no specific requirement on the angle of the pump laser which gives much greater flexibility in the geometry of the setting and allows for fiber pig-tailing of the optical device or creating integrated planar circuits with it.

The researchers said they believe their breakthrough "pave[s] the way for on-chip circuitry with ultrafast, all-optical, logic operability."

To read more about the new transistor and how it works, go here.