COMETA: Co-planar Optical/RF beamforming via Integrated microwave Photonics and metasurfaces

Beyond-5G and 6G systems require compact front-ends supporting high-capacity wireless links, adaptive beam steering, resilient operation, and multifunctional sensing. Current approaches based on microwave photonics, optical phased arrays, free-space optical (FSO) communications, RF antennas, and metasurfaces have demonstrated remarkable capabilities, yet they remain largely independent subsystems, increasing footprint, losses, power consumption, and packaging complexity. COMETA proposes a breakthrough co-designed RF–photonic shared aperture simultaneously transmitting optical and RF signals, engineering integrated photonics, photoconductive functional layers, optical metasurfaces, RF resonators, and radiating structures into a unified electromagnetic platform. At the core of the architecture is a low-loss silicon nitride photonic integrated circuit acting as a common signal-distribution, synchronization, and control infrastructure. The photonic layer routes coherent optical tones toward free-space optical emitters and photoconductive regions, enabling simultaneous optical beam generation, RF generation through optical photomixing, and optically controlled electromagnetic tuning. The project introduces a modular architecture of COMETA cells, each combining emission, beamsteering, and wavefront control of optical and RF signals. Optical beam steering combines grating emitters and photoconductively controlled metasurfaces, while the RF branch exploits localized optical-to-RF conversion and compact resonant antennas enhanced by reconfigurable RF metasurfaces and cavity-assisted radiation. This enables a platform where optical and RF beams are generated, shaped, and steered in a coordinated manner. A major challenge is developing a multi-scale, multi-physics co-design methodology handling nanometric optical metasurfaces, micrometric photonic circuits, photoconductive materials, and millimeter-wave RF structures. COMETA will establish design rules, integration strategies, and validation methodologies for these strongly coupled subsystems, leveraging heterogeneous integration techniques such as transfer printing for the localized assembly of photoconductive materials onto silicon nitride photonic platforms. A proof-of-concept E-band (71–86 GHz) demonstrator will validate localized continuous-wave optical-to-RF generation, optical and RF beam steering approaching ±20°, and short-range RF/FSO transmission over 0.5–1 m laboratory distances. Beyond the demonstrator, COMETA establishes foundations for a new class of multifunctional RF–photonic front-ends where photonics, RF radiation, metasurface engineering, and photoconductive conversion form a single technological ecosystem. Bridging integrated and microwave photonics, metasurfaces, free-space optics, and RF engineering, COMETA advances the state of the art toward compact, adaptive, and scalable platforms for future communication, sensing, and hybrid RF–optical infrastructures.