Multi-photon near-infrared emission of Er3+ ions induced by upconversion self-sensitization of layered polarized Bi9V2O18Cl semiconductor with narrow-band

Abstract Due to the wide range of anisotropic properties, layered hosts that consist of two-dimensional (2D) platelets may endow the upconversion (UC) of rare-earth ions (RE3+) dopants with new optical properties different to traditional three-dimensional (3D) host. Here, we first reported a different UC construction mechanism of Er3+ ions triggered by Bi9V2O18Cl layered crystal that combines spontaneous polarization and narrow-bandgap. The solid-method prepared Er3+-doped Bi9V2O18Cl crystals that are connected by van der wars forces present individual micro-sheet and significant polarization property. Over the threshold power of a commercial 980 nm laser, a special two-photon near-infrared (NIR) emission of 4I13/2 level in Er3+ ions are observed without concentration dependence, accompanied by a special UC process that upconverting photon number of red emission is always over that of the green one. Experiment indicant that under the spontaneous inter electric field (IEF), efficient photocarriers separation in the narrow band-gap semiconductor makes a special band-to-band multi-photon process of Er3+ ions possible, being responsible for the unusual multi-photon NIR and UC appearance. The results of this study can provide new insights into the relationship between the material structure and UC of RE3+ ions and promote the potential applications of photon avalanche phosphors in solid-state lasers and optical switches.