Additive engineering of nonlinear optical properties of all-inorganic halide perovskites

In this study, ligand-assisted reprecipitation was used as a cost-effective and room-temperature synthesis method to produce CsPbBr3 and CsPbBr2I all-inorganic halide perovskites. CaCl2 were doped at four different concentrations into the nanocrystals to effectively engineer their nonlinear optical properties. The nonlinear responses of the prepared samples were investigated using the Z-scan technique under irradiation with a 632.8 nm He-Ne laser. Initially, the Z-scan method was examined theoretically, followed by both open- and closed-aperture Z-scan techniques to measure the nonlinear refractive (NLR) index (n2) and nonlinear absorption (NLA) coefficient (beta), respectively. The cubic perovskite nanoparticle morphology was observed via field emission electron microscopy. The size variation due to doping was analyzed using dynamic light scattering analyses. The particle sizes increased from 35 to 250 nm for CsPbBr3 and from 30 to 330 nm for doped CsPbBr2I. The self-defocusing NLR coefficient decreased from 9.3 to 4.8 x 10-8 cm2 W-1 for CsPbBr3 and increased from 5 to 13 x 10-8 cm2 W -1 for CsPbBr2I with the addition of Ca2+ ions. The NLA coefficient increased for both nanocrystals with higher doping levels. The enhanced saturable absorbing properties of doped halide perovskites suggest their potential application in Q-switching and mode-locking lasers.