Advanced Design and Control of Active and Passive Metamaterials : from Microwaves to Optics

Light usually passes through transparent materials in simple ways that science pupils learn at school. However, physicists have recently been examining the possibility of taking a normal transparent material, and inserting tiny metallic inclusions in various shapes and arrangements. As the light passes over these structures tiny currents are set up that generate electric and magnetic fields that modify the way the light travels through the material. The effects can be dramatic leading to slowing light to a few metres per second, or to bending light in very unusual ways / so-called negative refraction. These effects are potentially very useful in all kinds of ways that are only beginning to be understood. Lenses that break traditional diffraction limits are one possibility. An 'invisibility cloak' another. At the more mundane level, the wavelengths that we will be focussing upon (mm) are expected to enhance the performance of cellular telephone networks, designed to handle large area, mobile applications personal communication services/networks, global positioning systems, broadcast satellite television, satellite phone services and automotive electronics. Waves in this part of the spectrum have a fabulous information capacity. The highly directive nature of mm-wave beams, the predicted small size and lightweight of the hardware are also great advantages. The main desire is to unify more than one function in an application (e.g. antenna/filter/generator or amplifier). The progress towards higher frequencies, coupled to miniaturization, increases the bandwidth and information capacity. The metallic inclusions are much smaller than the wavelength of light so that as far as the light is concerned the material with inclusions behaves as a uniform effective medium, or a meta-material. The research is therefore a concerted theoretical platform activity aimed at creating the best design and understanding of metamaterials obtained so far. We will be focussing on design solutions that will address some of the known problems associated with metamaterials as well as others not known at this stage. Loss is a major issue that we will address through the design of metallic inclusions that are actively controlled by applying external currents. Salford will address loss control and elimination by using active diode additions to traditional ring and omega particle structures. Chiral, or handed, inclusions will provide smart artificial molecules that are expected to have completely new properties. These expectations will require new and deeper insights into the equations that describe how electromagnetic fields interact with matter, and so will be extended to embrace the ideas of nonlinearity (i.e. output is not proportional to input) and nolocality (memory). Surrey will adopt a specific modelling approach that will bridge the gap between methods used at the microscopic nanomaterials level and techniques previously used for macroscopic multilayered structures. They will examine ordered/disordered arrays of inclusions as conceived by Salford. Surrey will pursue new ideas of using metamaterials to slow down light that rely on geometry rather than resonance effects. Imperial will address fundamental aspects related to plasmonics. Issues of definition also need to be addressed so that our code will be written with the utmost robustness and reliability.