Ultrafast linear and Nonlinear Interactions for photoinduced Chirality in nanophotonic devices

• Applicants: Professor Dr. Giancarlo Soavi; Professor Dr. Andreas Tittl
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 577521545

Chirality in nanophotonic systems has emerged as a powerful mechanism to manipulate the polarization and spin of light. However, achieving dynamic chirality control on ultrafast timescales remains a major challenge. The UNIC project aims to pioneer all-optical control of linear and nonlinear chirality using hybrid structures composed of dielectric metasurfaces and layered van der Waals (vdW) materials. The consortium brings together leading Brazilian (UPM and CNPEM) and German institutions (LMU and FSU) to explore the interplay between metasurface engineering, excitonic dynamics in 2D materials, and light-matter interaction at the nanoscale. Our central strategy is to create active chiral platforms by leveraging photo-induced symmetry breaking. We will pursue three interconnected objectives: (1) Design and realize active metasurfaces where chirality can be switched ON and OFF on a picosecond timescale. This will be achieved by optically breaking the symmetry of a novel “restored symmetry-protected chiral bound states in the continuum” (RSP-BICs), transforming a photonically achiral ground state into a strongly chiral one. (2) Integrate tailored vdW materials and heterostructures (e.g., twisted bilayers, chiral crystals) with metasurfaces. This will enable optically controlled circular dichroism (CD) by photo-exciting electronic or excitonic populations in the 2D material, with the metasurface providing strong resonant enhancement of the chiroptical response. (3) Achieve all-optical control of nonlinear chirality. We will investigate the active modulation of nonlinear CD in hybrid and monolithic structures. We will exploit the interference between the nonlinear response of the photo-activated BIC and the excitons in the layered material to create new degrees of freedom for controlling chiral light. By combining cutting-edge experimental and theoretical methods and leveraging the synergistic expertise of the consortium spanning nanofabrication, ultrafast spectroscopy, theoretical modeling, and 2D materials synthesis, UNIC will deliver a new class of miniaturized, high-speed chiral photonic devices. These advancements will pave the way for novel applications in quantum optics, tunable light sources, and next-generation optical information processing.

• DFG Programme: Research Grants
• International Connection: Brazil
• Partner Organisation: Fundaçao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP
• Co-Investigator: Professor Leonardo de Souza Menezes, Ph.D.
• Cooperation Partners: Professor Dr. Dario Bahamon; Dr. Alisson Cadore; Professor Dr. Christiano de Matos