Radiation and guidance of metasurface-waves - Prof. Stefano MACI - UNISI - Italy
In the recent years, metasurfaces (MTSs), i.e. the two-dimensional equivalent of Metamaterials (MTMs), have been in the spot-light of the EM research. On one hand a MTS can be faced as a 2D design/analysis problem which can be handled much more easily than a 3D problem; on the other hand, a MTS has the appealing characteristics of low profile, manufacturing simplicity, combined with the capability of control of the EM field. MTS are composed by an arrangement of small metallic/dielectric inclusions of different shape in a regular lattice inside or printed on a dielectric thin layer. They can be realized with standard PCB technologies or additive manufacturing. The BCs perceived by an EM field can be modified at will by spatially changing the characteristics of the small inclusions in a gradual manner. We identify three main design of MTSs: (i) space-wave designed MTSs; leaky-wave designed MTSs (ii) and surface wave designed MTSs (iii). Space-wave designed MTSs control impinging spatial waves by refracting, deflecting, focusing or controlling the polarization of an impinging space wave. Among these applications, Huygens MTSs have gained attention. The second class of MTS is designed in order to covert a bounded surface wave (SW) into a curvilinear wavefromnt leaky-wave (LW): this is the case of MTSs for direct radiation, where impedance BCs are modulated in a locally-periodic fashion. MTSs for SWs manipulation control their propagation path, changing the SW wavefront and guiding the. Combining these different design into microwave devices leads to high-gain, low-crss pol antennas, Gaussian horns, multibeams, lenses, deflector, metaradomes, etc. Adaptive MTSs, composed of dynamically reconfigurable materials, would allow to explore new reconfigurable-beam antennas. Encompassing with imagination, the MTS could be interpreted as a conformal surface whose characteristics can be adapted time-to-time to the needs, changing arbitrarily the role of the surface or of its subparts from guiding structures to radiating devices.
Hyperbolic metamaterials : enhanced nonlinearity, Purcell effect and hot electrons - Prof. Anatoly ZAYATS- KCL - UK
The development of dielectric and plasmonic metamaterials and metasurfaces has led to numerous opportunities in designing unusual optical properties and applications. Hyperbolic metamaterials is a class of anisotropic metamaterials which can be constructed in all frequency ranges from UV to RF. Due to their specific isofrequency surfaces, they support high wavevector modes and are crucial for achieving high-resolution imaging, subwavelength waveguiding, enhanced nonlinearities and broadband Purcell factors in spontaneous emission. The optical properties of such metamaterials can be adjusted over a wide spectral range by geometrical tuning.
In this tutorial, we will first overview microscopic and effective medium theories of the optical properties of hyperbolic metamaterials [1-3], detailing the role of nonlocalities and epsilon-near-zero behavior [4,5]. The applications of such metamaterials in passive photonic devices, waveguiding [6-8] and bio- and chemical sensing will be discussed [9-11]. The approaches to achieving active and tunable metamaterial platform will be presented for engineering of the enhanced second-order [12] and third order (Kerr-type) [13-16] nonlinearities and related all-optical control of light intensity [13] and its polarization [16], as well as for designing local density of states and a broadband Purcell effect enhancement [17]. Electrically driven active hyperbolic metamaterials for hot-electron generation will also be discussed [18].
Multiscale disordered materials for photonics - Prof. Remi CARMINATI - ESPCI - France
Our approach is characterized by the joint use of numerical simulations and theoretical approaches to address different aspects of optics in complex media. Besides fundamental studies in mesoscopic optics (e.g. the transfer of information through opaque scattering media), we also study the potential of disordered materials for photonics applications. For example, we have shown recently that so-called hyperuniform disordered materials can exhibit transparency properties even at high densities, for which a fully disordered material would be opaque due to scattering. A feature of disordered photonic materials is their scalability and their robustness to fabrication imperfections.
From Quantum to EM modelling - Prof. Luca PIERANTONI - UNIVPM - Italy
The presentation deals with the multi-physics analysis/modeling of the combined electrodynamics-quantum transport in new-concept devices based on nano-structured materials. The latter include atom carbon nanotubes, graphene, 2D-beyond graphene, but also other atomically smooth surfaces as ferro-electrics and ferro-magnetic materials. The developed theoretical-computational platform deals with combined electromagnetic/quantum transport/thermal phenomena, bridging from discrete, atomistic (nano-scale) level to continuum (meso-scale) level. A key-development is in the fact that ab-initio simulations performed at atomistic level transfer/integrate the results into/with the larger scale models by constitutive equations/relations, to incorporate all necessary physics towards the full-wave simulation. In the case of ballistic transport, the Maxwell equations are self-consistently coupled to the Schrödinger/Dirac equations: the electromagnetic field provides sources terms for the quantum transport equations, that, in turns, provide charges and currents for the electromagnetic field. Examples of simulations focus on CNT/graphene, and other 2D-materials based devices, ferro-electric (HfO2) based devices, nano-opto-mechanical cavities.
Phononics and Optomechanics - Dr Francesc ALZINA - ICN2 - Spain
The first part of this lecture will describe the basics of elastic waves propagation in solids, emphasizing analogies and differences with electromagnetic waves. It will cover the fundamentals of continuum mechanics and the theory of elasticity. The examination of the solutions of the governing equations in an infinite medium, half-space, plate and layers will allow establishing a background of understanding from which the second part of the lecture will be derived. This second part will be devoted firstly to the control and manipulation of elastic waves in phononic crystals and metamaterials, and secondly to the interaction of elastic waves and photons in optomechanical crystal cavities. Accordingly, we will start studying phononic crystals and metamaterials in which the modulation of the elastic properties results in the modification of the phonon dispersion and, in some cases, in frequency band gaps due to the induced translational Bloch symmetry (Bragg scattering) or the hybridization between propagating waves and localized modes. Finally, we will introduce cavity optomechanics, which investigates the enhanced interactions of photons and elastic waves when co-localized in small volumes. This will be exemplified for structures that exploit the difference in electromagnetic and elastic waves velocities and allow the manipulation of both type of waves in the same length scale, although their very different frequencies.
Space-time modulated metamaterials and their applications in antennas and Doppler cloaks - Assoc. Prof Davide RAMACCIA - Roma 3 - Italy
In this lecture we will present the recent advancements in the field of space-time modulated metamaterials. Such materials are characterized by constitutive parameters that are modulated in both space and time through an external control. At first, the physical insights of the unusual interaction arising between the electromagnetic field and space-time modulated metamaterials will be presented, with a particular emphasis on the resulting non-reciprocal behavior that is achieved without using magnets. The fundamental principles behind the operation of space-time modulated metamaterials will be highlighted and the corresponding analytical-numerical framework will be presented. Finally, we will show how the artificial non-reciprocity achieved by using space-time modulated metamaterials can be exploited to design innovative non-reciprocal antennas and metamaterial/metasurface-based cloaking devices hiding the velocity of a moving object.
Multiscale EM modeling of metasurfaces and interfaces - Prof. Giuseppe VECCHI - POLITO - Italy (tbc)
Abstract
