2019 Thomas Young Medal and Prize
Professor William Barnes for his outstanding contributions to the development of nanophotonics, especially in plasmonics and nanoscale light-molecule interactions.
William Barnes was the first to show that monomolecular organic layers (Langmuir-Blodgett layers) are optically biaxial, in doing so he established a new polarization conversion technique that became a powerful way to analyse liquid crystal materials and devices.
At Exeter he and his group are known primarily for three major contributions. Barnes was the first to demonstrate a full photonic band gap. Looking at photonic band gaps for surface modes rather than bulk modes eased the fabrication requirements and allowed him to make the world's first demonstration of this important effect. Second, he was (co)first to report the experimental confirmation of narrow resonances in arrays of metallic nanoparticles due to coherent plasmonic effects. Third, he extended the concepts of cavity quantum electrodynamics into new territory. The use of confined light (eg in a microcavity, or associated with a surface plasmon) to modify the way molecules emit light was well established, indeed, Barnes has harnessed these ideas to improve the efficiency of light emitting diodes and to develop thin film lasers. However, his breakthrough was to show that confined light fields can be used to modify processes other than the emission of light, specifically he showed that it can be used to control the inter-molecular transfer of energy.
His present research is on two fronts. First, he is developing a new all-molecular pathway to making nanophotonic materials by showing that when dye molecular assemblies are formed into suitable structures they may exhibit confined light modes similar to the surface plasmons supported by nanostructured metals. Second, he is leading research to use confined light fields to radically alter the energy levels of ensembles of molecules. Ongoing research includes band-engineering the optical properties of carbon-based materials and manipulating the charge and energy transport of 2D molecular materials, including photosynthetic materials.