New polariton light – matter switch paves the way for faster more efficient opto-electronics
Greek researchers from the Institute of Electronic Structure and Laser (IESL) of the Foundation for Research and Technology-Hellas (FORTH), in collaboration with the Universities of Cambridge, UK and Mexico, have created a novel energy-efficient switch utilising a "liquid form" of light. The device could be a breakthrough in electronics providing unprecedented energy - efficient circuits.
The novel microscopic device has been fabricated in the Microelectronics Research Group of FORTH-IESL in Heraklion, Crete, Greece by a team of researchers led by Prof. P. Savvidis. The performance of the device was investigated in the University of Cambridge, UK. The device is a new optoelectronic switch that changes spin state at will through a weak electrical pulse.
Contemporary electronics use charges to process information internally and light to transfer it over longer distances (optical fibres). As technology evolves, the need for faster, more efficient devices has pushed electronics to the physical limits of field effect transistors (electrical switches), which are their main building blocks. That technology has served society over the past 40 years but is now fast approaching its limits urging scientists to identify alternatives towards faster more efficient circuits.
Information transfer over larger distances is achieved with light pulses. That technology requires fast emitters and detectors of light and combination of the two technologies to translate electrical signals to light pulses and vice-versa, thus adding complexity and high cost to the overall systems.
Polariton fluid emits clockwise or anticlockwise spin light by applying electric fields to a semiconductor chip.
Credit: Alexander Dreismann
In between the two, there is a state of half-light and half-matter with unique properties. Polaritons, as they are called, exhibit properties only found in photons and charged particles at the same time. One of their unique properties is the ability to form condensates “Bose Einstein”. In this form, polaritons behave as a liquid form of light that can be controlled efficiently by electric fields.
The spin of the condensate can be readily controlled by applying a small voltage over the micrometer-sized devices. The success of the method is many-fold. Not only is the result in the form of circularly polarized light, easily coupled to optical fibres, but the energy required to switch the spin state is very small, in the order of femto-Joules, as well.
Associate Professor Pavlos Savvidis of the Department of Materials Science and Technology of the University of Crete and Collaborating Researcher at FORTH-IESL who is leading the Greek team mentioned: “While the prototype device works at cryogenic temperatures, the researchers are developing other materials that can operate at room temperature, so that the device may be commercialised”. The other key factor for the commercialisation of the device is mass production and scalability. “Since this prototype is based on well-established fabrication technology, it has the potential to be scaled up in the near future”, said Prof. Savvidis.
“The polariton switch unifies the best properties of electronics and optics into one tiny device that can deliver at very high speeds while using minimal amounts of power” said the paper lead author, Dr. Alexander Dreismann from Cambridge’s Cavendish Laboratory. The work was published in Nature Materials.
The research team is currently exploring options for commercialising the technology as well as integrating it with existing technology base.