Superior third-order nonlinearity in inorganic fullerene-like WS₂ nanoparticles

Two-dimensional (2D) transition metal dichalcogenides (TMDs) attain increasing attention due to their exceptional nonlinear optical efficiencies, which hold promising potential for on-chip photonics and advanced optoelectronic applications. Planar TMDs have been proven to support orders-higher third-order nonlinear coefficients in comparison with common nonlinear materials. Interestingly, stronger light–matter interaction could be motivated when curved features are introduced to 2D TMDs. Here, a type of inorganic fullerene-like WS₂ nanoparticles is chemically synthesized using hard mesoporous silica. By using the spatial self-phase modulation (SSPM) method, the nonlinear refractive index n₂ and third-order susceptibility χ⁽3⁾ are investigated in the visible range. It is found that n₂∼10−⁵ cm²∕W and χ⁽3⁾∼10−⁷ esu, two orders higher than the counterparts of planar WS₂ structures. Our experimental findings provide a fresh thinking in designing nonlinear optical materials and endow TMDs with new potentials in photonic integration applications.