Imperial College London


Faculty of Natural SciencesDepartment of Physics

Reader in Physics



+44 (0)20 7594 7576r.oulton




914Blackett LaboratorySouth Kensington Campus






Light and the various ways it interacts with matter is our primary means of sensing the world around us. It is therefore no surprise that many technologies are based on light; for example submarine optical fibres form the backbone of the Internet and display technology now delivers affordable and compact crystal clear television. However, light itself has a limitation that we are still trying to overcome: light cannot be imaged or focused below half its wavelength, known as the “diffraction limit”. To see smaller objects we must use shorter wavelengths. e.g. Blue-ray, uses blue lasers (405 nm) to decode smaller infromation bits that store more information than DVDs, which are encoded using longer wavelength red lasers (650 nm). Today, we are learning to overcome this limit by incorporating metals in optical devices. My research investigates the use of metals to shatter the diffraction limit for creating new technological products, expand the capabilities of computers and the internet and deliver new sensor technologies for healthcare, defense and security.

We often take for granted just how strongly light can interact with metals. Electricity, oscillating at 50 Hz (essentially very low frequency light), has a wavelength of thousands of kilometers, yet a wall-plug is no larger than a couple of inches; well below the diffraction limit! The relatively new capability to structure metal surfaces on the nanoscale now allows us to use this same phenomenon to beat the diffraction limit in the visible spectrum. Metals do this by storing energy on the electrons that collectively move in unison with light, called surface plasmons. This approach has recently re-invigorated the study of optics at the nano-scale, feeding the trend to smaller and more compact technologies.

So what sets nano-optics aside from low frequency electricity if they share the same physics? I believe the paradigm of nano-optics is the capability to reduce the size of visible and infrared light so that it can occupy the same nano-scale volume as molecular, solid state and atomic electronic states for the first time. Under natural conditions the mismatch makes light-matter interactions inherently weak and slow. With nano-optics, interactions not only become stronger and faster but weak effects once difficult to detect are dramatically enhanced. This goal of this proposal is to strengthen such weak effects and utilize them to realize new capabilities in optics. Exploring optics at untouched length scales is an exciting opportunity giving us the potential to make fundamentally new discoveries.

Plasmonic Lasers

Plasmon Laser beyond the   diffraction limit


Metamaterial Lasers


Semicondcutor Plasmonics


Prof. Carsten Ronning, University of Jena, Nano Optics of Semiconductor Nano Crystals, 2010 - 2015

Prof. Xiang Zhang, University of California, Berkeley, Plasmonics and Metamaterials, 2010 - 2015

Guest Lectures

How to make a laser smaller than the diffraction limit, Institute for Solid State Physics, University of Jena, Jena, 2011

Lasers beyond the diffraction limit., Imperial College London, London, UK, 2010

Plasmonic Environments for Enhanced Light-Matter Interactions, Department of Electrical Engineering and Computer Science, University of California at Berkeley, Berkeley, CA USA, 2008