An international research collaboration led by the University of Southampton has demonstrated tiny vortexes of twisted light that will enable higher capacity data transmission in optical computing.

The innovation, which uses microgears to twist light around an axis much like a corkscrew, makes use of chemical element germanium that is compatible with the silicon used to make computer chips.

Southampton researchers together with partners from the University of Tokyo, Toyohashi University of Technology and Hitachi Ltd, all in Japan, have described the new light-emitting gears in The Optical Society journal Optics Express. With a radius of one micron or less, 250,000 of these gears could be packed into just one square millimetre of a computer chip.

Lead author Abdelrahman Al-Attili, of Southampton’s School of Electronics and Computer Science, explains: “Our new microgears hold the potential for a laser that can be integrated on a silicon substrate— the last component needed to create an integrated optical circuit on a computer. These tiny optical-based circuits can be based upon the principle of twisted light, which makes it possible to transmit larger amounts of data.â€?

In conventional computing, light is used to carry information by varying the number of photons emitted or switching between light’s two polarisation states. With twisted light, or orbital angular momentum, each twist can represent a different value or letter, allowing the encoding of more information using less light.

This new research, which was supported by the Engineering and Physical Sciences Research Council (EPSRC), avoids the poor light emission efficiency qualities of silicon by expanding upon the material properties of germanium. The solution features microgears that are stretched by an oxide film.

“Previously, the strain that could be applied to germanium was not large enough to efficiently create light without degrading the material,â€? Abdelrahman says. “Our new microgear design helps overcome this challenge.â€?

The researchers used electron beam lithography to fabricate the very fine physical features that form the gears’ teeth. They then illuminated the gears with a standard green laser. After the microgear absorbed the green light it generated its own photons that circulated around the edges, forming twisted light that reflected vertically out of the gear by the periodic teeth.

The researchers optimised their design using computer simulations that model the way light propagates in the gears over a period of less than a nanosecond. By comparing a prototype’s light emission with computer simulation results, they were then able to confirm that the gears generated twisted light.

The researchers are now working to further improve the efficiency of light emission from the germanium microgears. If successful, this technology would make it possible to integrate thousands of lasers onto a silicon chip for transmitting information.

“Silicon fabrication technologies that were developed to make electronic devices can now be applied to make various optical devices,â€? Abdelrahman says. “Our microgears are just one example of how these capabilities can be used to make nano and microscale devices.â€?

Wireless communications expert Professor Lajos Hanzo has featured in Clarivate Analytics’ Highly Cited Researchers 2018 for the significant influence of his career over the past decade.

The Head of the Next Generation Wireless Research Group is one of 11 academics from the University of Southampton to be highlighted by the report, which recognises exceptional research performance from multiple papers that rank in the global top 1% by citations.

Lajos is among just 5 researchers based in the United Kingdom and only 96 worldwide included specifically for the field of Computer Science, although his subject is wireless communications.

He has built an international reputation for telecommunications in over three decades at Southampton’s School of Electronics and Computer Science (ECS) and Southampton is now the top-ranked university for Telecommunication Engineering in Europe according to the 2018 ShanghaiRanking's Global Ranking of Academic Subjects.

Lajos says: “It’s been a huge privilege to collaborate with a team of 119 talented PhD students in ECS and a similar number of academic colleagues over the decades – sincere thanks for the enlightenment I gained from our deep-routed discussions, in particular to Professors Sheng Chen (ISI Highly-Cited), Rob Maunder and Lie-Liang Yang, as well as to Drs El-Hajjar, Soon-Xin Ng and Rong Zhang.â€?

The Clarivate Analytics list of Highly Cited Researchers for 2018 identified scientists and social scientists across 21 fields used in Essential Science Indicators (ESI). The report surveyed papers published and cited between 2006 and 2016, ranking entries in the top 1% by citations for their ESI field and year.

The 2018 list contains 6,078 Highly Cited Researchers, including 2,020 researchers identified as having exceptional performance across several fields.

Two other researchers from Lajos’ Faculty of Engineering and Physical Sciences also appear in the list. Professor Mark Sullivan (who has recently been announced as the new Head of Physics and Astronomy) is featured in the field of Space Science, while Professor Nikolay Zheludev is honoured for his cross-field expertise within the Zepler Institute for Photonics and Nanoelectronics.

Lajos’ international career has included academic posts in Hungary, Germany and the UK. He has co-authored 18 John Wiley/IEEE Press books totalling around 10,000 pages on mobile radio communications. Earlier this year, he was awarded his second European Research Council (ERC) Advanced Fellow Grant totalling €2.5 million to contribute to the conception of the wireless Quantum Internet.

Four academics from the School of Electronics and Computer Science have been named Fellows of The Alan Turing Institute as part of a new cohort from the University of Southampton.

Professors Elena Simperl, Mike Wald, Sarvapali Ramchurn and Dr George Konstantinidis will address complex research challenges within the UK’s national institute for data science and artificial intelligence.

The researchers are among 19 leading academics at the University that will now bring to the Institute specific projects covering topics from machine learning for space physics to AI and inclusion.

The Alan Turing Institute was founded in 2015 to undertake world-class research that is applied to real-world problems, drives economic impact and societal good, leads the training of a new generation of scientists and shapes public conversation around data.

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