A chameleon-like core-shell organic/lanthanide flexible crystal waveguide for bandwidth and colour tunability

Optical fibers capable of dynamically generating and/or transporting narrow/broadband spectral signals in the visible spectral region based on the input light, much like how a chameleon changes its color, are quintessential for developing visible light communication devices. Here, we demonstrate a mechanically flexible, blue-violet fluorescent 2-(4,4'-bis(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)biphenyl) (BPP) crystal waveguide surface coordinated to red fluorescent Eu(tta)₃. The BPP microcrystal waveguide, acting as the core, with BPP-Eu(iii) as the shell, provides a hybrid platform for broad and narrow band signal transmission. Depending on the input light and the absorption of the core or shell, the crystal acts as an active-active, passive-active, or passive-passive light-generating and/or transporting optical waveguide. Notably, the pseudo-plasticity of the core-shell hybrid waveguide enables modulation of the signal output direction without compromising its optical performances. The development of such smart optical waveguides has enormous potential for visible light communication and selective light-based microprecision sensing applications.