Lead-Sulfide-Based Hybrid Inorganic-Organic Superlattice Particles for Prominent Nonlinear Optical Absorption

Simultaneously optimizing nonlinear absorption coefficient and modulation depth is a considerable challenge for nonlinear optical materials. Here we present an effective solution through constructing PbS2-based inorganic-organic superlattice. PbS2/Cn superlattice particles are synthesized, where n (4, 6, and 8) denotes the number of carbon atoms in the organic component. First-principles simulations indicate the formation of covalent bonds and van der Waals interaction between PbS2 unit and interlayer organic molecules. All samples exhibit strong nonlinear absorption under femtosecond laser excitation with a wavelength range between 515 nm and 900 nm, and the nonlinear absorption coefficient increases with interlayer distance. The optimized sample, PbS2/C8, demonstrates outstanding nonlinear absorption and substantial modulation depth under 800 nm (the third-order nonlinear absorption coefficient beta eff, 10449 +/- 609 cm GW-1; modulation depth, 39.1%) and 900 nm (the fifth-order nonlinear absorption coefficient gamma eff, 6465 +/- 68 cm3 GW-2; modulation depth, 88.1%), which exhibits saturable absorption under 515 nm (beta eff, -4932 +/- 818 cm GW-1; modulation depth, 48.1%). It exhibits a small optical limiting threshold of 1.23 mJ cm-2. These performances surpass those of typical single-/few-layer metal chalcogenides. Structural and spectral analyses elucidate that the remarkable optical nonlinearity can be attributed to quantum confinement in the inorganic layer and the dielectric enhancement of the superlattice.