On-Crystal Optical Modulator from Polarized Propagation of Lanthanide-Titanium Nanoclusters

The orientation and magnitude of optical polarization in trivalent lanthanides (Ln³⁺) depend on the directional arrangement of individual transition dipole moments (TDMs), rendering great difficulty in achieving polarized propagation that is highly determined by the packing symmetry and the compositional coordination in atomic precision. Here, we obtained crystals of the organic-monolayer protected titanium-alloyed lanthanide nanoclusters (i.e., Eu₈Ti ₁₀ NCs), where the TDMs of Eu³⁺ ions generate typically orthogonal polarization behaviors (i.e., π/σ-light) from the ⁵ D₀→ ⁷ F _1,2 transition. Most importantly, the Eu₈Ti₁₀ single crystal presents a remarkable polarized propagation with unprecedented anisotropy relevant to the crystallographic axis, thus resulting in an on-crystal optical modulator.