School information

- Many thanks to all the Lecturers and Attendees!

A course of the European School on Metamaterials will be held right after the Conference (20 - 21 September 2019). The lectures will be held in the campus of the "Niccolò Cusano" University, which is easily reachable from the conference venue by public transport (more details on the School Venue here).

The school topic is:

Spatial, temporal and phase control in Metamaterials and Metasurfaces: New frontiers in wave tailoring

General Chairs: Prof. Mirko Barbuto and Prof. Davide Ramaccia

The course will be focused on emerging engineered artificial materials whose electromagnetic, optical and acoustic properties are dynamically controlled in space, time and phase. The recent interest in this topic is motivated by the possibility to engineer both the spatial and temporal characteristics of the wave interacting with these materials almost at will, opening up possibilities to envision new wave phenomena and create new devices.

The school offers a unique opportunity to students and young researchers to meet pioneers and leading experts in metamaterials and get exposure to the latest advancements in this burgeoning research field. Comprehensive lectures will take into account the widespread backgrounds of the audience.

Lecturers:

Andrea Alù - Spatial and Temporal Modulations for Wavefront Control with Metasurfaces

Mirko Barbuto - Real-time control of phase singularities for wave tailoring at microwave frequencies

Isabelle Staude - Tunable dielectric metasurfaces and metadevices

Nader Engheta - 4D Metamaterials

Davide Ramaccia - Modulated metamaterials and metasurfaces and their applications to antennas and Doppler control

Vicent Romero-Garcìa - Control of the acoustic waves in the subwavelength regime: metamaterials for perfect absorption and metadiffusers

Sergei Tretyakov - Introductory tutorial on metasurfaces for control of reflection and transmission

Lecture abstracts:

Andrea Alù: I will discuss the basics of wavefront manipulation using metasurfaces, first for passive, linear, time-invariant systems, pointing out the limitations and potentials of this technology for various applications, and then expanding to nonlinear, time-modulated and active material platform, which enables going beyond these limits. I will discuss theoretical limits, and practical implementations at radio-frequency and optical frequencies, and provide an overview of possible venues for future research in these areas.

Mirko Barbuto: The manipulation of phase singularities carried by vortex fields is an emerging research field aiming at obtaining unusual amplitude and phase distributions of an optical beam, with potential applications ranging from manipulation of microscopic particles to communications or imaging systems. Typically confined to optical frequencies, recently it has been extended to microwaves but practical applications in this frequency range are still under investigation. In this lecture, we explore the generation and manipulation of phase singularities at microwave frequencies and we show how their topological properties can be exploited to control in real-time the radiation properties of antenna systems. In particular, first we provide the general mathematical framework for the analysis of the phase singularities generated by standard radiating elements. Then, we present a new design tool for tailoring their radiation properties based on the topological properties of phase singularity points. The design of some configurations of practical interest will be presented.

Isabelle Staude: Optical metasurfaces composed of designed Mie-resonant semiconductor nanoparticles arranged in a plane provide comprehensive control over the properties of light fields. However, the optical response of most semiconductor metasurfaces realized so far was permanently encoded into the metasurface structure during fabrication. Recently, a growing amount of research is concentrating on obtaining dynamic control of their optical response, with the aim of creating metasurfaces and metasurface-based devices (“metadevices”) with functionalities that can be tuned, switched or programmed on demand. Mie-resonant dielectric metasurfaces are particularly attractive in this regard, since their strongly dispersive behavior as well as the resonant enhancement of the optical near-fields inside or near the nanoresonators facilitate active tuning of their optical response.
This lecture will overview the state of the art of research into tunable dielectric metasurfaces and metadevices. Following a general motivation of this research area, the fundamental concepts regarding the optical properties of subwavelength dielectric nanoresonators will be established. To this end, I will discuss Mie-resonances of dielectric nanoparticles and analyze how they are influenced by the nanoparticle shape, size, material composition, and environment. I will then briefly introduce the concept of dielectric Huygens’ metasurfaces, before focusing on graded Mie-resonant dielectric metasurfaces for wavefront control applications in more detail. The central part of this lecture will then discuss various strategies to render the metasurface response tunable and reconfigurable on demand, and review recent progress in the actual experimental implementation of these strategies. Finally, potential applications of tunable dielectric metasurfaces and metadevices as well as open challenges are discussed.

Nader Engheta: In this lecture, I will discuss some of the properties of wave propagation in the four-dimensional (4D) metamatarials, i.e., structures with spatiotemporal variation of the materials parameters. In particular, I will present some of the fundamental features of waves in media with rapid temporal variation of relative permittivity, and explore some of physical constraints associated with the energy of the waves and medium. Several examples involving passive and active media will be presented.

Davide Ramaccia: 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.

Vicent Romero-Garcìa: The ability to control an incoming wave field in a sub-wavelength material is advantageous for several applications in wave physics as energy conversion, time reversal technology, coherent perfect absorbers, or sound-proofing among others. The solution of this challenge requires to solve a complex problem: reducing the geometric dimensions of the structure while increasing the density of states at low frequencies and finding the good impedance conditions for the desired control. In this talk I present the possibilities of a new type of sub-wavelength metamaterials based on the concept of slow sound propagation. This last type of metamaterials makes use of its strong dispersion for generating slow-sound conditions inside the material and, therefore, drastically decreasing frequency of the absorption peaks. Hence, the structure thickness becomes deeply sub-wavelength. These open systems, at the resonant frequency, are characterized by both the leakage rate of energy (i.e., the coupling of the resonant elements with the propagating medium) and the intrinsic losses of the resonator. We discuss in this talk, the different possibilities offered by the balance between the leakage and the losses to activate the condition of critical coupling for trapping the energy around the resonant elements and generating a maximum of energy absorption or to generate deep subwavelength diffusers, what we call metadiffusers.

Sergei Tretyakov: In this introductory lecture I will give the definition of metasurfaces and explain their basic functionalities. The lecture will start from definitions and history, explaining the role of electric and magnetic polarizations, bianisotropy, and nonlocality for realizing properties needed for various applications. The main learning outcome of this lecture will be understanding of what physical properties of metasurfaces are responsible for various field transformations and knowledge of typical cell topologies which are suitable for realization of desired metasurface properties.

School time schedule

More information here.