Abstract
This paper establishes the potential of the recently introduced ABX(3) metal-free perovskite structures for third-order nonlinear optical processes. The base unit in this family of materials is an ammonium halide octahedra, and it incorporates a large aromatic cation spacer forming the classic perovskite structure. This work shows that the choice of cation is key to the resulting third-order nonlinearity, where the incorporation of "MDABCO" into the structure, a very polar cation, results in a third-order nonlinear refractive index on the order of 10(-17) m(2) W-1 and high laser damage threshold of 0.8 J cm(-2). Owing to its very wide band gap of similar to 5.12 eV, this material exhibits a high nonlinear figure of merit across the visible and near-infrared transmission windows. These results show that the metal-free family of perovskite materials is an excellent candidate for nonlinear optics in the important visible and near-infrared wavelength regimes.