Anagrafe della ricerca

The ambitious objective of METEOR is the development of a new platform for TeraHertz generation, based on an optical-rectifying metasurface (OR-MTS) and its direct integration in a TeraHertz metasurface (THz-MTS) for molding a radiated beam with ad-hoc features. Our idea takes inspiration from the recent discoveries of the involved research groups on harmonic generation in non-metallic nanoantennas (nanoresonators), and on metasurface antennas and their modeling. The key concept is to fully exploit the possibilities offered by metasurfaces of different length scales to first generate THz radiation and then manipulate the emitted signal. The novelty that we introduce is twofold: first, we aim at showing THz generation in all-dielectric optical metasurfaces with unprecedented efficiency, targetting to enhance the THz generation power by more than three orders of magnitude compared to the state of the art of optical rectification; second, we aim at showing for the first time how to combine two different metasurfaces with non comparable length scales to extract the THz and generate a structured beam. In other words, we aim at having an active THz integrated antenna with unprecedented power emission and beam control. Moreover, our methodology of handling and co-designing the optical and THz functional layers, and the proposed combined use of metasurfaces, introduces a new paradigm. This will have a remarkable impact as a technological innovation and scientific challenge. Recent results have proven that high-index AlGaAs dielectric nanoparticles, supporting nontrivial optical modes which originate from the physics of bound states in the continuum (BIC), can boost the efficiency of second-order nonlinear interactions; for this reason, our OR-MTS is based on nano-engineered all-dielectric nanoantennas. The THz collecting and radiating MTS is based on an all-metal pillars structure whose effectiveness has been recently proved, and its design will include the OR-MTS, acting as a distributed THz source. The fundamental physics involved in the development will meet exceptional theoretical challenges: 1) a new formulations for BIC-based interaction between optical bounded waves and THz- waves aimed to estimate the conversion efficiency; 2) a new formulation for matching the bandwidth of the pulsed laser input to the THz-MTS space-modulation functional layer for increasing the overall efficiency; 3) a customized multiscale numerical optimization. Fabrication and experimental challenges will be faced to validate the demonstrator, comprising an active THz high-gain, high-efficiency antenna with optical tunability of central frequency.