Chris Stevens BA DPhil

Chris originally qualified as a Physicist in 1994 and worked in Italy as a Human Capital Mobility Fellow (Universitat degli Studi di Lecce) where he helped develop a new laboratory for studies of semiconductor devices.

He subsequently returned to Oxford and pursued research into the basic physics of high temperature superconductors using ultrafast optoelectronic probes to determine superfluid relaxation rates and the speed with which the superconducting state is established.

Chris moved to Engineering in 1998 with a Royal Academy of Engineering Senior Research Fellowship and developed a group working in optical heterodyne techniques and ultrafast electronics. Since 2000 he has been a Fellow of St Hugh’s college and a University Lecturer in Engineering Science.

In his spare time, Chris spends quite a lot of time underwater.

Chris’ research area is Ultrafast Electronics which is a rapidly developing field in which he explores the ultimate speed limits of electronics. He uses a wide variety of techniques to manufacture novel circuits and systems. One among these is the laser micromachining tool.

This field engages a wide range of disciplines and requires expertise in RF circuit layout, novel condensed matter physics, superconductivity, optics and quantum properties of matter. In order to evaluate the performance of ultrafast electronic systems Chris has to develop new methods for analysing electromagnetic signals. A lot of the research in his group has so far centred on this basic problem. They have developed methods for current and voltage sampling in superconducting circuits, and a new instrument – the ultrafast STM which enables probing of nanoscale electronic components with sub picosecond time resolution.

A recent addition to the portfolio is development of metamaterial devices for a variety of high frequency applications including NMR microscopy, ultra high Q RF filters and ground penetrating radar. They are currently developing methods to design metamaterial devices to break the Abbe limit and utilize the interactions between microwave signals and living tissue to perform medical imaging.

A second and increasingly important research area is the development of magnetic metamaterials for contactless data transfer and for power distribution. These two capabilities will enable a host of applications and technologies including wireless power for electronic devices and systems, and the replacement of backplanes and wired connections between integrated circuits themselves. This is a project Chris calls Electronic Lego.

Future developments include new nanowire electronic devices further pushing the speed limits or electronic systems and nanoelectronic photovoltaic cells which exploit the extremely high surface area available from nanotextured surfaces to make highly efficient and low cost solar cells.

Metamaterial Devices

Over the last ~15 years a gradual increase in interest in the applications of metamaterials has spawned a new research interest here in the development of Magneto-Inductive Wave Devices  for a variety of high frequency applications including NMR microscopy, Ultra High Q RF filters and Ground penetrating Radar.  In particular, Chris is very interested in the development of MIW structures as data connectors, power distribution networks and for electrical machinery.

Ultrafast Electronics

Chris' original research area is Ultrafast Electronics which is a rather catch-all term for research into the ultimate speed for electronic devices and systems. This field engages a wide range of disciplines and requires expertise in RF circuit layout, condensed matter physics, superconductivity, quantum properties of matter and materials science. In order to evaluate the performance of ultrafast electronic systems we have to develop new methods for analysing electromagnetic signals.

Much of the work in the group to date has centred on the development of new techniques with which to investigate circuit performance at >100GHz speeds where conventional circuit analysis techniques are impossible to implement. We have developed methods for current and Photokinetic Sampling,  and the ultrafast STM (funded by the Royal Society) which enables probing of nanoscale electronic components with sub picosecond time resolution. Current work includes te development of a Terahertz impedance analyser.

Communications

In addition to his work on electronics, Chris is very active in the allied area of ultrawideband (UWB) communications and electromagnetics with current projects investigating the propagation of UWB signals in a variety of environments. One significant area is the development of wireless backplane technologies for small and medium scale electronics assemblies. Typical cost for back-planes in mobile base stations for instance is often in excess of $4000. Removing the need for this component increases flexibility and reduces costs.

He has a strong interest in the imaging possibilities presented by UWB signals and systems, particularly from the high contrast nature of their interaction with living tissue which has spurred a new research area in UWB medical imaging.

Chris is also active in low frequency electromagnetics with projects in contactless power transfer and TSS- Oxford KTP Project: Submarine Electromagnetics and Ultra-wideband communications.