Light and its various interactions with matter are our main means of perceiving the world around us. Photonics is the science that deals with the generation, detection and manipulation of light by emission, transmission, modulation, signal processing, switching or amplification. Conventional photonic/optical components are generally based on the simple principles of refraction, reflection or diffraction of light. The design of such components is generally conceived by considering the effects of light propagation through the constituting materials over distances typically much larger than the wavelength. Wavefront shaping is thus obtained by gradually accumulating changes in amplitude, phase and/or polarization along the beam path. As an alternative, metamaterials have attracted a lot of interest over the past two decades due to their unprecedented flexibility in handling electromagnetic waves. Metamaterials are artificially structured on a scale lower than the wavelength. They derive their optical properties not only from the intrinsic properties of the base materials, but especially from the precise geometry, size, orientation and arrangement of their structural elements. This allows for the design of optical materials with unexpected and sometimes specific properties, exceeding the limits of what can be achieved with existing materials. Several devices, such as super-lenses or cloaking devices, have been developed over the past decade based on this new metamaterial technology. By reducing the size of metamaterials to subwavelength thickness devices, it is now possible to modulate the direction of light, its polarization and intensity using a simple optical interface. The technology of flat optical components, also known as metasurfaces, will significantly change the design methods traditionally used for optical systems. The control of electromagnetic fields by nanostructured interfaces will have important repercussions in several areas such as lighting, imaging, displays and spectroscopy.
In the OPERA project, we are investigating and optimizing the properties of planar photonic devices based on metasurfaces using numerical modelling. The scientific and technical activities that constitute the project work programme are organized around 4 main workpackages. The numerical characterization of the optical properties of planar devices based on metasurfaces, as well as their optimization are at the heart of the activities and objectives of two horizontal (transversal) workpackages. These numerical methodologies will be integrated into the DIOGENeS software framework that will eventually integrates (1) discontinuous Galerkin-type methods that have been tested over the past 10 years for the discretization of Maxwell equations in time and frequency regimes, mainly for applications in the microwave band, (2) parallel resolution algorithms for sparse linear systems based on the latest developments in numerical linear algebra, (3) modern optimization techniques based on learning and metamodeling methods and (4) software components adapted to modern high performance computing architectures. Two vertical workpackages complete this program. One of them aims to demonstrate the contributions of methodological developments and numerical tools resulting from transversal workpackages through their application to diffusion/radiation control by passive planar devices. The other, more prospective, concerns the study of basic building blocks for the realization of adaptive planar devices.