Recent advances and perspectives on space-time coding digital metasurfaces

Within the overarching framework of space-time metastructures, digital metasurfaces based on spatio-temporal coding are emerging as powerful and versatile architectures for complex field manipulations, also in view of their inherently programmable nature. Here, we provide a compact survey of our recent results and ongoing studies in this research area. Examples of field manipulations include harmonic beam steering and/or shaping and programmable nonreciprocal effects. Possible applications are abundant and range from wireless communications to radars and imaging.

Second Harmonic Beam Shaping and Sensing in Dielectric Bow-Tie Antenna via Convex Optimization Array Synthesis Approach

We propose a convex optimization approach for an array synthesis pattern to enhance the electromagnetic field in the gap region of a dielectric bow-tie antenna. This method allows the induction of the desired antenna modes by exploiting the concurrent excitation of the structure with plane waves with different propagation directions and complex amplitudes. By engineering the excitation coefficients of the array, different modes are excited in the bow-tie antenna and the radiation pattern of the generated second harmonic (SH) field is modified accordingly. Using our approach, we demonstrate both the feasibility of performing synthesis of the SH radiation pattern in dielectric antennas and the possibility of developing innovative sensing applications in photonics.