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 PbS 2 -based inorganic-organic superlattice. PbS 2 /C n 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 PbS 2 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, PbS 2 /C 8 , demonstrates outstanding nonlinear absorption and substantial modulation depth under 800 nm (the third-order nonlinear absorption coefficient β eff , 10449 ± 609 cm GW −1 ; modulation depth, 39.1%) and 900 nm (the fifth-order nonlinear absorption coefficient γ eff , 6465 ± 68 cm 3 GW −2 ; modulation depth, 88.1%), which exhibits saturable absorption under 515 nm ( β 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.
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