Phase change material breakthrough bridges the gap between electronics and photonics

Researchers from the University of Southampton have demonstrated a new material family that will revolutionise optical circuits to replace parts of traditional electronic hardware.

The materials allow rapid reversible switching between two states, known as phase change, which has previously been limited to electronic circuits as standard commercially available materials suffer from large optical losses.

Scientists from the Quantum, Light and Matter group and Optoelectronics Research Centre (ORC) have designed the phase change materials to exhibit no loss of light at telecommunication wavelengths and be switched with very low power.

The technology is compatible with existing silicon photonic circuits and opens the door for more advanced applications. Researchers have published their findings in Advanced Functional Materials.

Lead authors Dr Matthew Delaney and Dr Ioannis Zeimpekis pinpointed the material structure and composition to enable high transparency while exhibiting low power modulation of light. They found that the new composition has 100 times less loss than the current state-of-the-art optical materials.

Their material was deposited on top of optical chips, where a short laser pulse was used to crystalize the material and change the phase of the guided light. The researchers demonstrated this property reversibly thousands of times. Importantly, the material remembers its last state without any applied signals, leading to large potential power savings.

Professor Otto Muskens, Head of the Integrated Nanophotonics group, says: “This new technology will simplify and enable newly emerging applications such as solid-state LiDAR, quantum and neuromorphic computing that are currently limited by the performance of the existing materials.

“Neuromorphic and programmable photonics are set to revolutionise the industry as they offer new paradigms for data processing going far beyond existing hardware. Quantum optical circuits are on the horizon and ultralow loss components are needed to make the next step in controlling and routing quantum information.”

Traditional communication electronics consume a huge proportion of their energy at the interconnection level, and their bandwidth is directly limited by the communication length. Using photons instead of electrons alleviates these shortcomings.

Phase change photonics offer much promise for the future of integrated silicon photonic circuits, with some of the world’s largest companies competing in the race for fully integrated optical solutions. However, the high absorption losses in current commercially available materials have prevented their use in larger photonic systems such as in interconnects between data servers, where the photonic technology is projected to excel.

Professor Dan Hewak, ORC co-author who has spent decades on phase change materials, says: “This is a significant breakthrough for optoelectronics. Our team has now demonstrated a material which bridges the gap between electronics and photonics and we expect to see further advances resulting from their discovery.”

The new phase change family has been designed as part of a series of research projects funded by the Engineering and Physical Sciences Research Council (EPSRC), including ChAMP, the Manufacturing and Application of Next Generation Chalcogenides (EP/M015130/1), Cornerstone (EP/L021129/1), The Physics and Technology of Photonic Metadevices and Metasystems (EP/M009122/1) and Nanostructured photonic metamaterials (EP/G060363/1). The new materials reside within the chalcogenide family as they combine antimony and sulfur or selenium.

The team is currently working to implement more photonic circuit components with the aim to design a neuromorphic computing photonic chip with in-memory computing capabilities. It is expected that this method will replace current technologies within the next couple of years enabling a leap forward for the technology of photonic computing.