Science & Technology

New highly energy-efficient optical “transistors” speed up calculations up to 1,000 times

An international research team led by Skoltech and IBM has created a highly energy-efficient optical switch that can replace the electronic transistors of a new generation of computers that operate photons instead of electrons. In addition to direct power savings, the switch does not require cooling and is very fast. With 1 trillion operations per second, it’s 100 to 1,000 times faster than today’s leading commercial transistors. This study was published on September 22, 2021. Nature..

“What makes the new device so energy efficient is that it only takes a few photons to switch,” commented Dr. Anton Zasedaterev, the first author of the study. “In fact, in our Skoltech lab, we achieved switching with just one photon at room temperature, but there is a long way to go before such a proof-of-concept demonstration can be used in an all-optical coprocessor. “Pavlos Lagoudakis, head of Hybrid Photonics Labs at Skoltech, added.

Since photons are the smallest particles of light that exist in nature, there is little room for further improvement in terms of power consumption. Most modern electric transistors require dozens of times more energy to switch, and transistors that use a single electron to achieve comparable efficiency are much slower.

In addition to performance issues, competing power-saving electronic transistors also tend to require bulky cooling, which in turn consumes power and impacts operating costs. The new switch works conveniently at room temperature, avoiding all these issues.

In addition to its key transistor-like functionality, the switch can act as a component that links devices by shuttleting data between devices in the form of optical signals. It also acts as an amplifier, increasing the intensity of the incident laser beam up to 23,000 times.

How to use

The device uses two lasers to set the state to “0” or “1” and switch between them. Use a very weak control laser beam to turn another bright laser beam on or off. The control beam only takes a few photons, which makes the device more efficient.

Switching occurs within the microcavity. It is a 35 nanometer thin organic semiconductor polymer sandwiched between highly reflective inorganic structures. The microcavity is constructed to trap the incident light inside for as long as possible to facilitate binding of the cavity to the material.

This combination of light and matter forms the basis of new devices. When a photon binds strongly to a bound electron-hole pair (also known as an exciton) in the material of the cavity, this results in a short-lived entity called an exciton-polariton. This is a kind of quasiparticle at the heart of the switch’s operation.

When the pump laser (the brighter of the two) illuminates the switch, it produces thousands of identical quasiparticles in the same place, forming the so-called Bose-Einstein condensate. It encodes the “0” and “1” logical states of. device.

To switch between the two levels of the device, the team used a controlled laser pulse to seed the condensate shortly before the arrival of the pump laser pulse. As a result, it stimulates energy conversion from the pump laser and increases the amount of quasiparticles in the condensate. The large number of particles there corresponds to the “1” state of the device.

Researchers have made some adjustments to ensure low power consumption. First, efficient switching was assisted by the vibration of the semiconductor polymer molecules. The secret was to match the energy gap between the pumped and condensed states to the energy of a particular molecular vibration in the polymer. The team then found the best wavelength to tune the laser and implemented a new measurement scheme that enables single-shot condensate detection. Third, the control laser that seeds the condensate and its detection scheme matched in a way that suppresses noise from the device’s “background” radiation. These measures maximized the device’s signal-to-noise ratio and prevented excess energy from being absorbed by the microcavities. This helps to heat the device only by molecular vibrations.

“Currently, pump lasers that keep the switch on are the mainstream, and there is still some work to be done to reduce the overall power consumption of the device. The route to that goal is with us with our collaborators. Perovskite supercrystalline materials, such as those sought in, are good candidates because they provide a strong collective quantum response in the form of superfluorescence due to the strong light-material binding. It has been proven, “commented the team.

In a larger plan, researchers consider the new switch to be just one of the growing toolkits of all optics assembled over the last few years. Among other things, it includes a low-loss silicon waveguide for reciprocating optical signals between transistors. The development of these components brings us closer than ever to optical computers that operate photons instead of electrons, delivering exceptional performance and low power consumption. Research at Skoltech was supported by the Russian Science Foundation (RSF).

Reference: “Nonlinearity of a single photon at room temperature” by Anton V. Zasedatelev, Anton V. Baranikov, Denis Sannikov, Darius Urbonas, Fabio Scafirimuto, Vladislav Yu. Shishkov, Evgeny S. Andrianov, Yurii E. Lozovik, Ullrich Scherf, Thilo Stöferle, Rainer F. Mahrt, Pavlos G. Lagoudakis, September 22, 2021 Nature..
DOI: 10.1038 / s41586-021-03866-9

New highly energy-efficient optical “transistors” speed up calculations up to 1,000 times New highly energy-efficient optical “transistors” speed up calculations up to 1,000 times

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