In 1836, H.F. Talbot introduced his eponymous effect with this sentence*: Although so much has been explained in optical science by the aid of the undulatory hypothesis, yet when any well-marked phenomena occur which present unexpected peculiarities, it may be of importance to describe them, for the sake of comparison with the theory.
Almost two centuries later, it is astonishing to think that all the reported observations that have deeply contributed to the foundations of optical science are based on simple optical devices like lenses, prisms and gratings – which are essentially hand-manufactured using workshops tools. Nowadays, nano-fabrication techniques like Electron Beam Lithography allow us to reproducibly fill the tiny space within the wavelength of light with engineered structures of negligible thickness, allowing unprecedented configurations for light structuring and manipulation. This is the new toolset of Planar Optics. The key elements for this new era of optics are metasurfaces: devices made of engineered nano-elements, designed to control the amplitude, phase and polarization of light.
The importance of planar optical devices is twofold. On one hand, they enable unique light coupling and molding for unprecedented optical functionalities. On the other hand, their reduced dimension is immediately in line with the quest for the compactness of modern lightweight consumer electronics which includes, cameras for computers and mobile phones, as well as visors for augmented and virtual reality. However, the same nano-fabrication processes, by which the metasurfaces are manufactured, also sentence them to the lacking tunability of a fixed design.
The ERC consolidator project METAmorphoses (funded by the European Research Council) aims to push the limits of planar optical devices in terms of tunability, by developing optical devices capable of transforming and adapting for on-demand optical functionality. We imagine lenses that according to specific user needs, can morph into gratings and later switch back into lenses.
*Reference: The London and Edinburgh Philosophical Magazine and Journal of Science, Third Series, Vol. 9 (1836)