Plasmonic Nanocavity-Assisted Long-Range Dipole-Dipole Interactions for Rare-Earth Ions.

Xie, Xin; Kang, Bowen; Hu, Huatian; Guo, Lei; Zhang, Min; Gou, Chengxiang; Kang, Ke; Li, Wangze et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Trivalent rare-earth ions (RE<sup>3+</sup>) exhibit sharp 4f-4f transitions that are highly sensitive to dipole-dipole interactions (DDIs), yet the intrinsic short-range of DDIs restricts their application in long-distance quantum coupling. Here, we demonstrate a plasmonic nanocavity pair that simultaneously couples to upconversion nanoparticles (UCNPs) and quantum dots (QDs), enabling enhanced emission and inter-emitter interaction. The combined effects of Purcell enhancement and surface plasmon polariton (SPP) propagation extend the DDI-mediated energy transfer over a record distance exceeding 7.5 μm, 2 orders of magnitude longer than conventional Förster resonance systems. Moreover, the polarization-controlled SPP propagation directs the in-plane energy redistribution, achieving anisotropic and tunable coupling. This work establishes a viable route toward controllable, long-range DDIs among rare-earth emitters, advancing integrated quantum photonic architectures.