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Photonic Metamaterials: From Basic Research to Applications

Final Report Summary - PHOTOMETA (Photonic Metamaterials: From Basic Research to Applications)

The main goal of the PHOTOMETA project was to investigate Negative Index Metamaterials, Tunable Metamaterials (MMs), Photonic Crystals, Plasmonics, and Casimir forces in a unified way, aiming to identify the main challenges of the fields, to propose specific approaches to attend them, and to study unexplored capabilities of those metamaterials. More specifically, the project objectives were: (a) Designing and realization of 3D optical metamaterials, and novel metasurface designs. (b) Understanding and reducing the losses in optical metamaterials by incorporating gain and electromagnetically-induced transparency (EIT). (c) Achieving highly efficient PC nanolasers and surface plasmon lasers. (d) Using chiral MMs and surface plasmons to reduce and manipultate the attractive Casimir and optical forces. (e) Using MMs, combined with nonlinear materials, for THz generation and tunable response. The unifying link in all these objectives is the endowment of photons with novel properties through imaginative use of electromagnetic (EM) field/artificial matter interactions.
Towards the achievement of the above objectives we developed different advanced simulation techniques (e.g. Finite Difference Time Domain method incorporating gain media, thin film and chiral metamaterials retrieval procedures for extraction of effective parameters of thin films and chiral media respectively etc.), and we employed them in detailed simulations, accompanied in many cases by careful experiments, which have led to some important achievements. Some of those achievements are the demonstrations of: (a) loss compensation in optical metamaterials by incorporating gain; (b) novel compact, highly controllable, efficient and low threshold lasers based of dark modes in dielectric metamaterials; (c) a novel system able to give under certain conditions repulsive Casimir force; (d) a variety of graphene-based metamaterials for THz applications (e.g. THz filter, modulator, tunable absorber, etc); (e) strong, broadband THz generation in Split-Ring Resonator metamaterials exploiting the non-linear properties of metals; (f) possibility of achieving toroidal dipolar response in dielectric metamaterials; such a response is offered for realization of new platforms for sensing, enhancing non-linearity, or even cloaking; (g) approaches to combine toroidal response in dielectric MMs with other elementary electromagnetic excitations (e.g. magnetic, dipolar-electric, etc.), expanding and advancing thus the toroidal-response based possibilities; (h) switchable chiral THz metamaterials offering great wave polarization control; (i) an approach for achieving metasurfaces offering broadband phase control (modulation larger than 2pi, with constant (high) amplitude) of the reflected or transmitted wave; such metasurfaces offer great possibilities for achievements of ultrathin optical components (for focusing, wave-steering, etc) and for broad-band group delay; the possibility and conditions to achieve parity-time symmetric chiral metamaterials; they can offer great advancement in the generation and control of circularly polarized waves; (i) high-quality resonant optical metamaterials by exploiting the dark modes of dielectric resonators, and avoiding the high losses inherent into metals.
Regarding photonic crystals, we demonstrated also extremely low-threshold lasing in 2D finite photonic crystals (PCs), exploiting not only the modified density of states provided by the PC but also the easily engineerable modal reflectivity at the interfaces between the PC and its surrounding medium. Moreover, we demonstrated both theoretically and experimentally directional emission, frequency splitter operation, and beam collimation with enhanced transmittance in finite 2D photonic crystals and PC-based structures by modifying properly the structure termination.
All the above results, which have been communicated in many papers and many conferences, pave the way for novel metamaterial and PC related components. Such components can be exploited in a variety of applications, including low threshold lasers, novel components for THz generation and manipulation, novel platforms for beam shaping, steering and manipulation, novel platforms for sensing, security and energy harvesting, and in many other applications areas where wave-matter interaction is a key issue.