Wide-Band-Gap Metal-Free Perovskite for Third-Order Nonlinear Optics

This paper establishes the potential of the recently introduced ABX3 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 m2 W–1 and high laser damage threshold of 0.8 J cm–2. Owing to its very wide band gap of ∼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.