Defect‐Engineered Layer‐Dependent Nonlinear Optical Response in 2D Muscovite for Efficient Optical Limiting

Abstract Light–matter interactions in 2D materials gain significant interest due to their distinctive optical and electronic properties. Recently, silicates emerge as a promising new class of 2D materials, but their nonlinear optical properties remain largely unexplored. This study demonstrates the layer‐dependent nonlinear absorption and optical limiting capabilities of 2D muscovite, a silicate mineral, using femtosecond laser excitation at 450 nm. The two‐photon absorption (TPA) coefficient is highly sensitive to the number of layers, increasing markedly from (3.91 ± 0.06) ×10 3 cm GW −1 in multilayer structures to (6.94 ± 0.17) × 10 5 cm GW −1 in the monolayer limit at a peak intensity 68 GW cm −2 , highlighting a pronounced layer‐dependent enhancement in nonlinear absorption. Additionally, monolayer muscovite exhibits an optical limiting threshold of 1.46 mJ cm − 2 , outperforming graphene and other 2D dichalcogenides. This enhanced TPA results from quantum confinement and intrinsic lattice defects that facilitate nonlinear optical transitions. Density functional theory reveals that liquid‐phase exfoliation disrupts potassium interlayers and induces oxygen vacancies, creating mid‐gap electronic states that significantly enhance TPA. These insights open new avenues for designing low‐fluence, high‐efficiency optical limiters using 2D silicates.