The field of ‘metamaterials’ has seen a tremendous growth in recent years, because of its ability to induce physical responses absent in nature, including invisibility cloaks and super-resolution lenses.

Conventional metamaterials rely on the spatial tailoring of the properties of small inclusions in a host medium. However, it is becoming increasingly viable and attractive to integrate active elements (such as diodes) so as to dynamically reconfigure the properties of the inclusions. This brings about a new temporal dimensionality, within the emerging concept of ‘space-time metamaterials’.

In a recent study [1], we have demonstrated theoretically and experimentally a two-dimensional planar electromagnetic metamaterial (‘metasurface’) based on spatio-temporal coding. In its simplest form, the electromagnetic response of each element can be switched via a diode between two possible states (e.g., in-phase and out-of-phase reflection), which can be associated with the 0/1 bits.

The switching is controlled in space and time by an integrated circuit (FPGA), according to a given coding which can be designed and optimized so as to perform a desired manipulation. For instance, for a given impinging beam, the metasurface can re-radiate multiple beams, steering different frequencies along desired directions, in a precise, controllable fashion, which may find interesting applications in high-capacity multiple-input-multiple-output communication systems. Alternatively, an incident beam can be spread across all possible directions and the whole frequency spectrum, which could be very useful for the reduction/control of scattering signatures as well as for novel computational-imaging schemes that are currently being explored for airport body scanners.

Within the proposed externship project, the MIT student will become familiar with the basic physics and modeling aspects of metamaterials. Moreover, he/she will develop a small project on the modeling and design of a simple space-time metamaterial, working in a team composed by two faculties, a postdoc and a PhD student, who will guide him/her through the various steps.

The supervisor, Prof. Vincenzo Galdi, is an internationally renowned scholar in the fields of electromagnetics and metamaterials. He has held several visiting positions at abroad research institutions, including the European Space Research and Technology Centre (Noordwijk, NL), Boston University, University of Texas at Austin, Massachusetts Institute of Technology, and California Institute of Technology. He is a Fellow of the IEEE, and the author of hundreds of publications.

[1] Zhang et al. “Space-time-coding digital metasurfaces,” Nature Communications 9, 4334 (2018).