Nonlinear optical limiting properties of multi-mechanism composite materials: principles, advances, and challenges

Nonlinear optical (NLO) limiting materials are essential for laser protection and advanced photonic applications. Metals, semiconductors, carbon-based nanomaterials, and organic macrocycles (e.g., porphyrins and phthalocyanines) exhibit distinctive limiting effects through mechanisms such as plasmon resonance, two-photon absorption, and excited-state absorption processes. Composite systems further enhance performance via interfacial coupling, achieving broadband operation, reduced thresholds, and ultrafast response dynamics. However, challenges remain, including the scarcity of broadband materials, poor dispersion stability, and the use of toxic fabrication methods. Future progress will rely on interdisciplinary strategies integrating molecular engineering, interface control, and device integration to realize efficient, stable, and environmentally sustainable optical limiting technologies.