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)BiI₄ 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.