Scientists from Heidelberg and St Andrews work on the basics of new light sources from organic semiconductors
With their research on nanomaterials for optoelectronics, scientists from Heidelberg University and the University of St Andrews (Scotland) have succeeded for the first time to demonstrate a strong interaction of light and matter in semiconducting carbon nanotubes. Such strong light-matter coupling is an important step towards realising new light sources, such as electrically pumped lasers based on organic semiconductors. They would be, amongst other things, important for applications in telecommunications. These results are the outcome of a cooperation between Prof. Dr Jana Zaumseil (Heidelberg) and Prof. Dr Malte Gather (St Andrews), and have been published in “Nature Communications”.
Organic semiconductors based on carbon are a cost and energy-efficient alternative to conventional inorganic semiconductors such as silicon. Light-emitting diodes consisting of these materials are already ubiquitously found in smartphone displays. Further components for application in lighting technology, data transmission and photovoltaics are currently at the prototype stage. So far, however, it has not been possible to produce one important component of optoelectronics with organic materials – the electrically pumped laser. The main reason is that organic semiconductors have only limited capacity for charge transport.
Prof. Zaumseil explains that research over the past few years has increasingly focused on laser-like light emission of organic semiconductors based on light-matter coupling. If photons (light) and excitons (matter) are brought to interact sufficiently, they couple so strongly that they produce so called exciton-polaritons. These are quasi-particles that also emit light. Under certain conditions, such emissions can take on the properties of laser light. Combined with sufficiently fast charge transport, exciton-polaritons could bring the production of an electrically pumped carbon-based laser within reach, according to Jana Zaumseil who is the head of the Nanomaterials for Optoelectronics research group at the Heidelberg University’s Institute for Physical Chemistry.
Thanks to the cooperation between Prof. Zaumseil and Prof. Gather, it was possible for the first time to demonstrate the formation of exciton-polaritons in semiconducting carbon nanotubes. Unlike other organic semiconductors, these microscopically small, tube-shaped carbon structures transport positive and negative charges extremely well. PhD student Arko Graf, the first author of the study, explains that exciton-polaritons also display extraordinary optical properties. The scientists in Heidelberg and St Andrews see their research results as an important step towards realising electrically pumped lasers on the basis of organic semiconductors. Prof. Zaumseil emphasises: “Besides the potential generation of laser light, exciton-polaritons already allow us to vary the wavelength of the light emitted by the carbon nanotubes over a wide range in the near-infrared.”
A revolutionary piece of technology, created by researchers at the University of St Andrews, can detect what an object is by placing it on a small radar sensor.
The device, called RadarCat (Radar Categorisation for Input and Interaction), can be trained to recognise different objects and materials, from a drinking glass to a computer keyboard, and can even identify individual body parts.
The system, which employs a radar signal, has a range of potential applications, from helping blind people identify the different contents of two identical bottles, to automatic drinks refills in restaurants, replacing bar codes at checkout, automatic waste-sorting or even foreign language learning.
Designed by computer scientists at the St Andrews Computer Human Interaction (SACHI) research group, the sensor was originally provided by Google ATAP (Advanced Technology and Projects) as part of their Project Soli alpha developer kit program. The radar-based sensor was developed to sense micro and subtle motion of human fingers, but the team at St Andrews discovered it could be used for much more.
Professor Aaron Quigley, Chair of Human Computer Interaction at the University, explained, “The Soli miniature radar opens up a wide-range of new forms of touchless interaction. Once Soli is deployed in products, our RadarCat solution can revolutionise how people interact with a computer, using everyday objects that can be found in the office or home, for new applications and novel types of interaction.”
The system could be used in conjunction with a mobile phone, for example it could be trained to open a recipe app when you hold a phone to your stomach, or change its settings when operating with a gloved hand.
A team of undergraduates and postgraduate students at the University’s School of Computer Science was selected to show the project to Google in Mountain View in the United States earlier this year. A snippet of the video was also shown on stage during the Google’s annual conference (I/O).
Professor Quigley continued, “Our future work will explore object and wearable interaction, new features and fewer sample points to explore the limits of object discrimination.
“Beyond human computer interaction, we can also envisage a wide range of potential applications ranging from navigation and world knowledge to industrial or laboratory process control”.
The University of St Andrews is a public research university in St Andrews, Fife, Scotland.
It is the oldest of the four ancient universities of Scotland, and the third oldest in the English-speaking world (following Oxford and Cambridge). It was founded between 1410 and 1413 when the Avignon Antipope Benedict XIII issued a Papal Bull to a small founding group of Augustinian clergy. In post-nominals the university’s name is abbreviated as St And (from the Latin Sancti Andreae).
St Andrews is ranked as the fourth best university in the UK by the Guardian University Guide 2014, the Times Good University Guide 2014 and the Complete University Guide 2015. Its Physics and Astronomy programme is ranked second in the UK, after that of the University of Cambridge, by the Times University Guide. The Times Higher Education World Universities Ranking names St Andrews among the world’s Top 20 Arts and Humanities universities. In the 2012 National Student Survey St Andrews had the highest student satisfaction among Scottish Universities. St Andrews requires the 4th highest entry grades of any comprehensive university in the UK.
The University is located in the small town of St Andrews in rural Fife. In term time, over a third of the town’s population is either a staff member or student of the university. The student body is notably diverse: over 30% of its intake come from well over 100 countries, 15% from North America; The University’s sport teams compete in BUCS competitions., and the student body is known for preserving a variety of other traditions.
St Andrews boasts five Nobel Laureates: two in Chemistry and one each in Peace, Literature and Physiology or Medicine.