Chiral Bismuth Halide Metasurfaces for Enhanced Second Harmonic Generation

Hybrid organic–inorganic metal halides have emerged as versatile materials for optoelectronics due to their outstanding optical properties and solution processability. Among these, chiral bismuth halides combine strong second-order nonlinear susceptibility with improved stability and reduced toxicity, making them attractive for nonlinear nanophotonics. However, efficient second-harmonic generation (SHG) in thin films is limited by weak light-matter interaction. Here, we overcome this limitation by integrating a chiral bismuth iodide ( R -MBA)BiI 4 with a nonlocal metasurface supporting guided mode resonances in visible and infrared ranges. The metasurface is directly fabricated using a versatile and scalable femtosecond laser ablation technique. We demonstrate that the resonant metasurface enhances SHG in comparison to the unpatterned film. This work establishes a new platform for efficient nonlinear photonic devices based on solution-processed nontoxic and cost-efficient materials.