Photoluminescence of simple arylbenzenes with ready synthetic accessibility is enhanced by two orders of magnitude through aggregate formation; viscosity and temperature effects indicate that the emission enhancement is due to the restriction of their intramolecular rotations in the solid state.

The optical properties of several distinct series of nonlinear optical (NLO) halide crystals with potential applications in the mid-infrared (mid-IR) spectral region have been investigated systematically using a first-principles computational methodology. The crystals have different NLO-active units [MX_k] (M = center cation, X = halide anion, and k = 6, 4, 3 or 2) and by combining atomic-level analysis with optical design considerations, their prospects for mid-IR applications are evaluated. The preferred microscopic structural units, which result in a relatively large NLO response and high laser damage threshold, are proposed. The study provides first principles guidance in the selection and design of novel halide crystals for mid-IR NLO applications.

K₂BiI₅O₁₅and Rb₂BiI₅O₁₅are synthesized and contain a unique [I₃O₉]³⁻bridging anionic group. Their powders show phase-matchable SHG effects 3 times that of KDP and the laser damage thresholds of 84 and 72 MW cm⁻², plus wide transparent range and good thermal stability.